First we NEED to know what version or build you are having the problem with? Please read
http://www.pligg.com/forum/showthread.php?t=1425 .
Some folders were recently removed do to non use so I'm guessing it's a very recent build.
I'm testing the latest build available through svn at
http://svn.sourceforge.net/viewvc/pligg/trunk/ and do not receive any error like that.
Jitgos