Maximum File Number Limit

I have a “maximum file number limit” on my account, and cannot upload files.
I’m only using around 4% of my disk space, and have never heard of such a limit.
But it’s real - I am shut down from using ftp.
Dreamhost doesn’t advertise this limitation on its users, and I can’t find any reference to it by searching the forum or the wiki. It has taken me over 2 days of looking for problems with my software, ftp programs, ISP and whatever, only to finally discover this strange Catch 22 at Dreamhost.
Can anyone tell me what it is about, and how to manage it?
Does it mean my account has been topped out at Dreamhost and I need to either open another account or move elsewhere?
I suppose there is a simple solution, but right now I hope you will forgive me for feeling as though someone is changing the rules on the fly here, and making a mockery of the huge storage and bandwidth promises.
It’s not a lot of fun to have sites in a shambles due to partial uploads and not being able to do anything about it.