I have FileManager installed on 2 computers - paid account.  While I can log in from one, Filemanager (using the same account login info) just keeps trying to connect from the other, so I can't synchronize files.  Any troubleshooting suggestions?  Using XP Pro SP2, IE 7, Netgear wireless router (though both computers are connected by wire to the router), with a Westell DSL modem.  Odd thing is, that computer used to connect OK - not sure what has changed - no changes my end, except an antivirus update (AVG).  I have tried logging out from the first computer - makes no difference - 2nd computer just keeps trying until I cancel, then it takes a few seconds for the "Connecting..." window to close.

Also, can DriveHQ FileManager be connected simultaneously from more than one computer using the same account on each?

DriveHQ FileManager doesn't limit on number of concurrent connections. So you can connect from any number of PCs.

Usually the problem is caused by anti-virus / network security software; also Internet Explorer session cookie should not be blocked as the logon session requires session cookie support.