Critical CSS regarding UIE Forum and "Aggregate and compress CSS files" option under Performance options

I love the UIE Forum module. I was really hoping to make these the default forums on my web site. I spent a lot of time to get it just how I wanted it. Then one day a week ago I decided to turn CSS caching on for Drupal under Performance options. It's the option that says "Aggregate and compress CSS files: Disabled Enabled".

After I enabled the "Aggregate and compress CSS files" option, it simply would not load any CSS files. I was going crazy the last week trying to figure out why. Finally today I simply disabled the UIE Forum module and suddenly it started to load the cached CSS files correctly.

Has anyone else had this issue? I'm sure I can't be the only option affected by this. I searched all the currently support tickets, but I couldn't find that anyone else had reported this same bug. Can you please tell me how I can fix this? I tried disabling other modules too. This issue seems to be caused specifically by the UIE Forum module. I love this module and I really want to get it to work. That's why I'm posting this bug request. I really need to use the cached CSS Performance option, because my site can take a long time to load, because it has to load CSS files from like five other modules, plus the theme module. It's much faster with this option enabled. If I can't find a solution to this issue, then I'm afraid I will need to go back to the default Drupal forum module. I don't really want to do that. :( I like UIE Forum because it has so many built-in options out of the box. Thank you.