Windows 7 network share is not accessible, handle invalid, 4672 4634

I have two Windows 7 PCs, no domain, same workgroup.

PC A used to be able to connect to PC B's network shares.Now it can't. Winf firewall on PC B is off for troubleshooting.

From PC A, double-clicking on PC B name in Explorer's network view prompts a login dialog box.

Login uses PC B\username on PC B, with correct password.

Error message is:

PC B is not accessible. handle is invalid.

Event viewer on PC B eventvwr winlogs\security shows the event ids:

4672 special logon

and immediately after it

4634 logoff logon type 3 (network)

So it appears PC A is using a valid user account and password to login to PC B, the login is accepted, but then the login is immediately logged off.

Using elevated cmd prompt on PC A, net view \\PC B returns

System Error 5 has occurred. Access is denied

The only thing I can think of that may have triggered this is that PC A was renamed using "Computer Properties" and restarted. The access problem began after this procedure.

Any tips on how to further troubleshoot this issue?