can't login to SSH as user, keep getting "-bash: fork: retry: Resource temporarily unavailable"

can't login to SSH as a user, keep getting "-bash: fork: retry: Resource temporarily unavailable" - but root login works. strangely, my webhost said the same user SSH login worked just fine for them, but it does not work when I try it ( My IP is whitelisted in our firewall too, so I don't think that's the problem)