Problem

Sometimes you might get a message from a server that you are blacklisted.

Details

First of all, this doesn't means you are blacklisted from the whole network nor has it any effect for the Kad network. The reason you might get such a message is that most servers have a build in spam/abuse protection, which tries to make sure that no client is using up too much ressources at once. If you do a lot searches within a short time or if you reconnect to the same server several times you could trigger this protection and the sever will refuse to communicate with you any further.
The easiest solution is to switch to another server. You can also wait some hours until the server lifts the ban, or just use the Kad network for this time.