Can't Log into ATT.Net

I am am member of a club which has a small website on att.net. They would like me to publish things from time to time. My ISP is SBCYahoo (DSL). When I try to connect, I get the following error message and my computer hangs up:

220 PWPFTPD 2.02 (6feb2002) Server (AT&T WorldNet (sm) Personal Web Pages FTP GIA server) [204.127.135.68]
AUTH SSL
234 AUTH SSL successful
Connected. Exchanging encryption keys...
SSL Error
The operation completed successfully.
Cannot login waiting to retry (30s)...

I've read everything I could on the att.net website. They say they allow other ISP's to access personal web pages if they use SSL encryption. I am using Windows XP with good memory, etc. Any ideas about how to fix the problem?? Thanks.

You have created a certificate and downloaded the last development build and all windows updates?

I have installed all of the windows updates and loaded the latest version of SmartFTP, but I still can't connect with att.net. I asked my son-in-law to try on his computer which is essentially equivalent to mine, but he uses attbi as his ISP (the old @home). It works fine. So the problem seems to be with my ISP -- SBCYahoo. I tried accessing on my other computer which uses Win98 and get the same message. It's hard to know who to ask for help since att.net is not my ISP and SBCYahoo won't help with att.net problems.

Settings->Connection->SSL

Enable "Use Client Cert" and a create a cert.

-Mat

I have created a client certificate and followed all of the steps listed at att.net's help site. My program still hangs up at "Exchanging encryption keys."

I can log onto commercial sites without difficulty. I am beginning to think it may have something to do with SBCYahoo. On their free website pages they do not allow ftp programs to upload. They require that you use their proprietary software called File Manager.