I had to reload Limewire on to my computer and now when I perform a video search, the only results I receive are 4-star quality when before I would get all results, regardless of quality. I have tried going into Options/Searching/Quality and have clicked on "Show All Qualities" but this changes nothing.

Thanks.

Does the same thing happen when you search for music?

Try this: Delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.