White screen under Drupal 5-7 with cache enabled

I'm having a white screen problem when I enable the cache on my Drupal 5.7 www.bpmtv.com site. I enable the cache normal. The site works great for a while, then when I log out of the superuser, the screen goes blank. Oddly, when I hit a different URL, such as bpmtv.com, without the www, it lets me back in to disable the cache and all works fine.

When I kill the memcached processes and restart them, it also fixes it. I'd like to find a reliable fix.

I've applied the appropriate patches views Drupal-5.7 and cck.

My settings.php file looks like this:

$conf = array(
'memcache_key_prefix' => 'bpmtv',
'swftools_media_url' => 'http://www.bpmtv.com', //
'cache_inc' => './sites/all/modules/memcache/memcache.db.inc',
'memcache_servers' => array(
'localhost:11214' => 'default2',
'localhost:11215' => 'page2',
'localhost:11216'=> 'filter2',
),
'memcache_bins' => array(
'cache' => 'default2',
'cache_menu' => 'default2',
'cache_page' => 'page2',
'cache_filter' => 'filter2',
),
);

I have the corresponding processes running locally. A ps -aux | grep memcached yields the following:

apache 2747 0.0 0.5 12704 11148 ? Ss 16:55 0:00 /usr/local/bin/memcached -u root -m 64 -p 11214 -u apache -d
apache 2748 0.0 0.3 7620 6068 ? Ss 16:55 0:00 /usr/local/bin/memcached -u root -m 320 -p 11215 -u apache -d
apache 2750 0.0 0.7 16840 15248 ? Ss 16:55 0:00 /usr/local/bin/memcached -u root -m 128 -p 11216 -u apache -d

On the same box, I have a Drupal 5.3 install. I've set it up in the exact same way. It is running memcached that does not cause the white screen issue. It leads me to believe that it might be a 5.7 issue.

I'm sure it's just an oversight on my part, but any help would be greatly appreciated.

In case it bears weight on the solution, here's the 5.3 config file:

$conf = array(
'memcache_key_prefix' => 'ichannel',
'cache_inc' => './sites/all/modules/memcache/memcache.inc',
'memcache_servers' => array(
'localhost:11211' => 'default',
'localhost:11212' => 'page',
'localhost:11213' => 'filter',
),
'memcache_bins' => array(
'cache' => 'default',
'cache_menu' => 'default',
'cache_page' => 'page',
'cache_filter' => 'filter',
),
);