I can access my Linux VPS with Putty but not a SFTP client

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http://serverfault.com – I am able to access my Cent OS 5.5 64-bit linux vps through Putty with no problem. But when I try WinSCP or FileZilla it just usually hangs on login. Sometimes I actually am able to login but then it hangs trying to display the first directory contents. Sometimes I get in for a few minutes, can transfer files, and then it hangs. I messed with all sorts of connection settings in both programs but no luck. What would cause these sort of random but frequent connection issues. Usually when I have a problem, Putty is open in another window (not always though) and that connection stays strong. M (HowTos)