Error on game install

I've been installing and testing games a few at a time on my test forum before putting them out on my live board.

Lately (since the last upgrade? - I don't remember the first time I saw it, sorry) I've been getting this error for each game:

Warning: fread() [function.fread]: Length parameter must be greater than 0 in /arcade/functions/tar.php on line 794

but the games still install, and apparently play alright (my partner and fellow Admin is testing them since I'm not much of a game player)