I haven't heard of that before except that reconnecting LW can mean connecting through different ultrapeers. Re-do the search, & also try browsing the person with the file. That can sometimes bring about finding more sources.

Using the manual search (& browse) I find are the best ways to find more sources.

You could try deleting your LW Preferences folder whilst LW is closed; instructions here: Fixes for Limewire to see if this has any effect. But make a note of your settings if you do this, b/c next time you open LW, you'll need to reset them.