.htaccess for multiple applications?

[eluser]WanWizard[/eluser]
This is indeed an infinitive loop, which mod_rewrite terminates after the limit has been reached.
Do what is suggested, create a rewrite log and bump the log level to 9, to see exactly what is going on.

And make it more clear what you are trying to achieve.

If you have two apps in the same root, you need to tell mod_rewrite exactly what needs to be rewritten. If both are using index.php hiding (or admin.php in this case), that might prove to be a challenge...