FTP keeps failing

I've started having recurring difficulty connecting to a
client's web server, and I don't know if the problem is on
my end or theirs. The server is an inhouse server, and the
webmaster isn't really very knowledgeable about
webservers.

Several days last week I had problems, though he said his
access was fine. Over the weekend I was in and out
repeatedly with no problems at all. Today I can't get in
again. He tells me he's not doing any work on the server
and nothing's changed. I'm pulling my hair out !!

Here are the error messages I'm getting. It's a Windows NT
server. I'm using WS_FTP and SmartFTP with Windows XP.
I've sent the webmaster these messages and he doesn't
know what the problem is.

If anyone can point me towards possible problems I'd
appreciate it.

(Using WS_FTP)--Sometimes I can't connect at all. I get:
! Receive error: connection reset
! Failed "port":
!Retrieve of folder listing failed (0)

Other times I make the initial server connection. When I
drill down to a subdirectory I get:
! Send error: connection reset
! Recieve error: connection reset
! Failed "port":
! Retrieve of folder listing failed (0)

(Using SmartFTP)--I make all connections, get in to the
subdirectory. When I try to upload my file I get:
Connection closed. Server timeout.
Command aborted. Server timeout.
An established connection was aborted by the software on
your host machine. Connection closed.