[Typo3] no access to install tool

[Christoph Koehler]

Hey there,

I just cleared my realurl cache tables, and for some reason, when in the  
backend, I don't get access to my install tool anymore. Instead I get the  
error message

Error. Reason: Segment "typo3" was not a keyword for a postVarSet as  
expected!

I didn't change my .htaccess file, so what could have caused this??

Thanks!

Chrstoph