Try this then:
Create a new style with no parent:
- Styles & Templates > Style Manager > Add New Style
- Parent Style: No Parent Style
- Title: Default vBulletin
- Allow User Selection: Yes
- Save
Then browse the site using that totally default vbulletin style - do you still have the same problem?
Also, did you look at the error_logs? (If you don't know where they are, ask your host.)
Also, when you write "shosin", do you really mean "suhosin"? If so, that is a server issue and your host will need to do something about it.