Theme broken apparently by saving Garland theme settings

I wasn't sure where to put this or what version to call it since it's happening on both 6.11 and 6.12, and I'm pretty sure it happened once before on an earlier version. Although I had just finished upgrading to 6.12 when it happened, it doesn't seem like that was relevant to the problem since my restoring the 6.11 backup had no effect, and I was able to reproduce the error in 6.11.

Essentially, what happened was that in my futile attempts to change the site logo to my own, rather than the default, I strayed into the Garland part of theme settings (www.mysite.com/admin/build/themes/settings/garland) thinking it might be overriding the Global settings. All I did there was untick the two boxes at the bottom "Use the default logo" and "Use the default shortcut icon", then click "Save configuration". Not only didn't my logo change, but by entire theme seemed to be stripped away, or at the very least its color. At the top of the page were these menacing messages, which I also attached in a screenshot:

* The selected file themes/garland/images/menu-collapsed.gif could not be uploaded, because the destination is not properly configured.

* The selected file themes/garland/images/menu-collapsed-rtl.gif could not be uploaded, because the destination is not properly configured.

* The selected file themes/garland/images/menu-expanded.gif could not be uploaded, because the destination is not properly configured.

* The selected file themes/garland/images/menu-leaf.gif could not be uploaded, because the destination is not properly configured.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/body.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-bar.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-bar-white.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-tab.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-navigation.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-content-left.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-content-right.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-content.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-navigation-item.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/bg-navigation-item-hover.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/gradient-inner.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/logo.png' for writing in /var/www/html/modules/color/color.module on line 502.

* warning: imagepng() [function.imagepng]: Unable to open 'files/color/garland-ff87c4d4/screenshot.png' for writing in /var/www/html/modules/color/color.module on line 502.

* The selected file /tmp/fileY2zaS2 could not be uploaded, because the destination is not properly configured.

* The selected file /tmp/file1z0S8g could not be uploaded, because the destination is not properly configured.

* There is a security update available for your version of Drupal. To ensure the security of your server, you should update immediately! See the available updates page for more information.

From that error, I managed to deduce there must be something amiss with the files/color/garland-ff87c4d4/ directory. Sure enough, when I went to check it out, the directory had a different number at the end of it (garland-b550d3d3 instead of garland-ff87c4d4), which is exactly what had happened last time. It seems like every time Garland is saved it randomly generates a new number for the directory, which it was having an understandably hard time referencing, since the name of the directory itself hadn't changed. In an effort to band-aid the problem, I changed the name of directory to reflect the one Drupal was looking for, and it worked fine.

While I can do my best to avoid messing with the logo for the time being and apply the same fix if need be in the future, a permanent solution probably wouldn't hurt either. I think the problem may stem from my attempt to clone Garland a while back to give myself an editable theme in case I should want to customize more than just the logo. I was pretty sure I followed the instructions I dug up on how to do it, and I had it working for a while until an earlier upgrade (possible from 6.10 to 6.11) wiped it out because I hadn't kept the Themes directory, mainly because the upgrade instructions hadn't mentioned it. It looks like there's some remnants of it though in an adjacent directory to the one with the problem (files/color/garboxfish-4877d574 -- garboxfish is my custom theme name), and there might be more strews around.

Sorry about the length of this, but I just want to get as much info down about it as I can while it's still fresh in my mind. Any ideas on how to properly fix this problem so it may be avoided in the future would be greatly appreciated. Thanks as always!

Alex