[TYPO3] Frontend rendering problems of content after some time?

[Michael Karrer]

Dear List,

i have a typo3 4.1.5 installtion with multi language and utf-8 enabled. 
Everything seems to be fine but after some time the frontend output is 
broken.

Clearing the frontend cache or the page cache does not help. But if i 
restart Apache and hit the reload button everything is back to normal?!?

I tried to disable any caching of apache and removed any php 
accelerators. What else could make my frontend break?!?

Please Help! Hints or thoughts are very welcome ;)