Incorrect stream wapper translation causes 404 in some situations

I had some trouble getting geshi filter language styles working, but only on the live server. This was because the location of the language CSS was being translated incorrectly and was creating a 404.

The file location of the geshifilter-languages.css should have been translated from

"public://geshi/geshifilter-languages.css"

to something like this

"http://www.example.com/sites/default/files/geshi/geshifilter-languages.css".

For some reason I couldn't figure out, this was being translated to the following on the live server.

"http://www.example.com/module/geshifilter/s/default/files/geshi/geshifil..."

I fix this I changed the drupal_realpath() and substr() combination to a single call to file_create_url(), which correctly generates the css file location in both my local dev and the live server.

Thanks,
Phil