XP Mode Computer Locking

I have XP Mode installed under 64-bit Windows 7. Whenever I key the letter "l" while in XP Mode, I get a popup window with a title bar of "Unlock Computer" which says "This computer is in use and has been locked. Only VirtualXP-95421\XPMUser (XPMUser) or an administrator can unlock this computer." That's followed by a field for "User Name" already filled in with "XPMUser" and a field for "Password" in which I have to enter my virtual machine password and then press OK. This occurs on all keypresses of the letter "l" regardless of whether I'm at the desktop or in a program, so that there's no way I can use the letter "l" normally! What is causing this ridiculous behavior, and how can I eliminate it so I can use "l" within XP Mode?

Just to clarify my original post, the key that's causing the "computer" to lock in XP Mode is the "L" key. Whenever "L" (either upper- or lower-case) is pressed, the popup windows requiring entry of a password appears. The "L" key is therefore totally unusable in XP Mode or any program run within it. I did do some searching here and elsewhere for any guidance on this problem but could find nothing. It effectively makes XP Mode unavailable, and I need it to run some legacy programs.

I had the same issue, solved pressing Windows key + L in the OS outside of XPMode, in my case, Win7 64.