A dog day afternoon, hot and humid and computer maintenance. I connected in to my office using Citrix virtual PC under Linux. I stepped away for awhile and the security setup locked the Windows 7 welcome screen. I tried all my tricks using Ctrl-F2 and Super keys. Finally, I discovered a virtual keyboard can be displayed from the welcome screen. Using that keyboard, I was able to enter the Ctrl-Alt-Del sequence and then my password. Back in business for another day.
I clicked on the ease of access button at the bottom left, checked the Type without keyboard box, then waited patiently. After a minute, the virtual keyboard on the right appeared, and I proceeded to mouse-click the Ctrl button, Alt button, and then the Del button revealing the password screen. Back in business after entering my password. Since I searched the internet forums in vain for this answer, I will add one more post about Citrix running under Linux.