PPS.  But at 50khash/s it would take you about five and half years to earn your first bitcoin.  Of course, it's far worse than that because the difficulty increases about every 2 weeks, so, really, you'll probably never earn a bitcoin.  I'd use that GPU for something else if I were you.

If it was working with poclbm I guess your network settings should be OK. CURL return code is a fairly generic code that means the HTTP response was >= 400, that can include not found, internal server errors etc and I'm not sure what deepbit would return if the authentication failed for some reason.

I can see you have "start" in the command line though and don't see a mention of that in readme.txt, so that would be worth removing in case it's trying to use the first parameter by default as a URL. Also I guess it wouldn't cause a problem but -gpu shouldn't be required, according to the documentation it should select the first GPU but I didn't have to use it for that version, I guess it's implied you want to use a GPU because you're running the CUDA version.

Try the following syntax, it's what I was using on deepbit fairly recently:

rpcminer-cuda.exe -url=http://deepbit.net:8332 -user=XXXXXXXXX@gmail.com -password=XXXXXXXX

The deepbit speeds are an approximation over time as it doesn't know the true speeds, what poclbm was reporting will be a more accurate number.