Windows 7 cPanel login problem

Has anyone else come across this problem?

I have just upgraded to a new windows 7 64bit machine and have been having problems logging into my cPanel managed sites with Internet Explorer 8.

Basically what happens is that at the login page a new window appears with the title "Windows Security" and the message "The server at (server name) requires a username and password" folloed by "Warning: This server is requesting that your username and password be sent in an insecure manner(basic authentication without a secure connection)". I duly enter my username and password for the site and it is deemed incorrect. The cPanel legacy login then appears and I enter the same credentials which are then accepted.

Most of the sites I manage via cpanel are with the same company but I have one which is hosted elsewhere and also has a cPanel. When I try to log into this one I immediately get the legacy cPanel dialogue and the credentials are accepted. With all the other sites however I get the Windows Security login dialogue first and this is what fails. Why would that be?

I have no problems with any other browsers, just IE8. I would be very grateful for any insite into this strange behaviour and if it is possible to do anything about it.

 

I found some information on the net which suggested that using the keyboard exclusively (no mouse) to enter the login details prevented this problem from occuring. Strange though that may seem, here are the results of some tests I have carried out both on my desktop and laptop machines, both running Win7 and IE8:

If I type in both username and password, authentication works
If I type in either the username and password but copy/paste the other item in with the mouse, it fails
If I copy either or both items with the mouse but paste in using Ctrl-V it works
If I copy either or both items with the mouse but use Shift-Insert to paste, it fails.

Using the mouse to select either box and/or submit does not alter any of the above.

Same behaviour on Desktop and Laptop machines.

I can't pretend to understand this behaviour but at least it is consistent. I suspect a bug?