4
You have an old PHP, can you upgrade?
I'll bet that if someone looks with mozilla/linux they will get a blank screen instead.
php.ini:
Register_Globals = Off/On ?
short_open_tag = Off/On ?
And your cache settings if any from Admin/System/Preferences
And just for kicks, what version of Xoops?
I've seen the same symptoms but I'm feeling much better now.