I'm having the same problem and I'm not sure if this helps but I started having this problem when I changed the main directory name that LW was installed in. Meaning....
Before, LW was installed in ~Online\Limewire and I changed the directory to !Online\Limewire.

LW would not work after that so I uninstalled/reinstalled it into the new directory and it still would not work. I uninstalled it again along with removing all LW entries in the registry and my .limewire directory in my profile.

Reinstalled and still installs in the task manager only.

I'm running WinXP with LW Pro 4.9.28 and I have tried running in Win2k mode also. Same thing.

I don't have the 'repair' option in the add/remove area so I can't try that.

I have not tried the Java upgrade (not sure where to do this) but I would not think this is the issue since everything was working fine until I changed the directory name.

Thanks for any help,
Debbie