I also have an easycap and have to deinterlace about 50% of the footage I capture. Sometimes it works perfectly, sometimes not. There doesn't seem to be any reason why. But what else do you expect from a $20 piece of plastic...
get this program called virtual dub im guessing your on windows http://virtualdub.sourceforge.net/
the clips will have some lines on them at times but u can fix that by rendering them all out in wmm and then editing the clips in your normal software that you would use for editing
L8 Media
Team Avid
if you have a Deinterlace Option called "Bob and Weave".... USE THAT ONE (think that one might be in virtual dub
I had a easycap too, but am on Mac so its a bit different
Ok, I'll look this, and try the next time.
thanks guys for your help