I figured this out too (a different solution)!
 

With the help of afisk, I also corrected the problem. Apparently, the problem is related to a really low value being stored for the height of the application window -- which makes sense given the solution posted above.

My own solution was a bit different. I deleted a hidden "limewire.props" file in a ".limewire" folder in the preferences folder. You can access this file via OS X's Terminal program. You can also use TinkerTool to reveal hidden files and folders, and then just drag it to the trash.

After I trashed this file, everything was fine, back to normal.

AFISK-- you need to change your name to kick'n-wing then to Kick'n-*** (that's what I'd do if I were you). Thanks for your help!

The 1-pixel-wide sliver is just below and as far left on the screen as possible. If you have a dark background you'll see it, if not you probably won't see it.

Again, thanks!
The Gimp

Lost Main Window (the solution)
 

Go in the monitor panel > change the resolution for largest then the main limewire window is back > resize it > come back to nominal resolution > it's OK