I certainly didn't comment about this b/c it's not an issue I've had to deal with on any frequency. Yesterday someone in the Mac OSX section of the forum also complained about this issue. I think I've had this happen only once.
One comment I will make though is that at 99% which could really mean anywhere b/w 99.0-99.99%, that you haven't lost much. Perhaps the last credits of the movie (probably less than 1 minute.) File verification may fail if there is simply 1 single bit or byte that doesn't match up.
You could try deleting your preferences folder whilst LW is closed to see if your prefs are semi-corrupted but still not sure this is the issue (see instructions here:
Fixes for Limewire.)
If this is happening with frequency I wonder if it's due to packet loss over your isp service or an anti-virus or firewall that's somehow changing the contents of your file. (I am aware of a website that offers packet loss testing but you need to sign up & pay a fee.)
(Also remember that a preview will duplicate that entire % of the movie that's been downlded at that time & place it in the incomplete folder with the word PREVIEW added to it.)