It's possible that it could be a false positive. Some programs produce them now & again. See here :

http://www.viruslist.com/en/glossary?glossid=153654932


It seems at one time I used Trend-Micro's antispyware & it would say that Limewire was spyware, somewhat similar to what Bullguard is doing for you. I'm not farmiliar with Bullguard (got these instructions from their forums) but try this: look under Antivirus > Protection, put a checkmark under Exclude Specific Files then click on Add Path. If you get the option to Browse then go down the list until you see Limewire , or you may have to copy/paste the actual target which would be this:

C:\Program Files\LimeWire\LimeWire.exe