Hey everyone, I'm a newbie miner mining with an NVIDIA 3100M

everytime I run my CGminer it displays:
Pool 0 slow/down or URL or credentials invalid
no servers were found that could be used to get work from

I have checked my mining pool URL http://pit.deepbit.net:8332
and the username is the same as the one when I registered to the mining pool

Could anyone tell me what should I do to get my CGminer worked, any further settings should I make?
Thanks a lot