Hi Juan, Terry, Georg, and anybody else who might be interested,
Sorry for the delayed response. I have been tied up with my job and finally got to troubleshoot tonight. The problem has been resolved! I first installed PixInsight on another computer with fairly similar hardware and identical operating system (Win7 x64) but with different applications and software. PixInsight worked perfectly on this computer. Therefore, PixInsight was innocent and my original computer used for image processing was the problem. I suspected a software conflict. To find the culprit, I opened "processes" under Task Manager and began to shut down any possible programs that might cause a problem. I would then reopen PI to see whether or not the problem was resolved. The software program that was conflicting with PI is called Roboform (a great program which I love but now must delete because I love PI more!). I deleted Roboform and now PI works perfectly! As I like Roboform so much, I'm installing it on my other computer which is not used for image processing. Terry, you might try this method on your computer. I first suspected my antivirus software, but shutting that down didn't solve the problem. But I kept on looking and finally stumbled upon the conflicting software.
Hope this helps someone,
Scott