I entered the exact title of some TV series and got no results at all from LW when you can get results from, say, e-donkey. Is it because of copyrights or something?

Also if you start searching for a specific video and enter the exact title you may get lots of results but it's impossible to download any. Bitzi tells you they have no bitprints for any of them (if you bother to check with many of them) when you know that they exist because they can be downloaded from e-donkey for instance, or a search from the Bitzi site turns out quite a number of results some of them are listed in the LimeWire search results and yet can't be downloaded (need new sources, it says)

No bitprints doesn't mean the file doesn't exist, just means nobody's rated it yet on Bitzi.

You have to search in different ways for some files. Vary your search terms a bit (try looking for actors' names or even director's name) & use the All Types search as well as Video. Search for title - avi (or whatever format you want). Search at different times of day when hosts in other time zones are online.

What's available on the network is constantly changing as people log on & off, add or delete files etc. Keep searching
LimeWire is just a Gnutella client... it can't ban videos. AFAIK, eDonkey uses the Overnet network... so you'll find different results than on Gnutella!
*Please just post once, multiple posts are a pain.