your probably not using Winrar 3.1 or whatever the latest is.
Other than that, i'm guessing you've got it from other means than emule? If so, it probably
is corrupt, or the file you've got isn't complete. In that case you need to get a replacement for the corrupt file (the one with the crc)
One of the many reasons why IRC is shit btw, you queue for hours, and then get shunned with crap
