Pretty urls and Fatcow
"The problem with your rewrites is that apache thinks "index.php/foo/bar" is supposed to be a file, but of course it isn't :)
I'd suggest trying either
RewriteRule ^(.+)$ index.php?/$1
RewriteRule ^(.+)$ index.php/$1 [R]
Note the question mark in rule 1 and the new R flag in rule 2."