Working fine now
After reading many forums and doing searchs (up late last night), I cleaned my cache & increased the screen timeout. Nothing helped until I pulled down and cut off a small strip from the top of my screen protector this morning. I remember reading that the proximity sensor is at the top right of the phone, looking at mine from the front, and putting my hand over it, it seems to be on the top left hand side.
Anyway it worked fine all day with several extended phone calls. My screen protector was about due to be replaced anyway, so when I get a new one I won't cut it. I expect that it will work well as long as the screen protector is in good condition as I just started having this problem recently. I was also thinking that many of us (at least me) have had the same screen protector on for quite awhile, maybe since the Droid first came out.
I hope this is all it was becaue I was losing my screen after every call that I didn't disconnect from, or when during a call, pulling it away from my face to turn on the speakerphone or dialpad. I'm hoping this is all it was but if it starts again, I'll let you all know. I hope this helps others!