Rockstar has released a new patch (Patch 7) for the PC version of Grand Theft Auto IV

The patch contains lots of bug fixes, crash fixes, graphics fixes as well as new graphics additions. There are some fixes to the multiplayer mod and the video editor too.

You can, if you like, download it from here:
http://www.fiberdownload.com/Transfer/Grand-Theft-Auto-IV/18454

Thanks, haven't played it much recently but good to know