[Typo3] Realurl forgets domain in links

[Johannes Reichardt]

Hey there,

I have an annoying problem and couldnt find somethin in the archives so 
far - i have a site running with virtual
directories and realurl but for some reason sometimes the urls forget 
the domain - so i have a link like

http:///directory/ instead of http://www.mydomain.com/directory/

When i manually clear the page cache its ok again - did anybody 
expirience something like this and knows a solution?

- Johannes