OE no start, another instance running

When I click to open OE6, I get this message: "Outlook Express could not be started because another instance of it is running on your computer. Please log off Windows and then restart ..." It adds that if this doesn't work, then reboot.
1. How do I log off Windows?
2. I have rebooted several times and still get the error message.
Any help appreciated.

 

Thanks, xflat. I have the latest updates and patches and I have that msoe.dll file, too.

 

Sorry. No, I am not, that is my OE, is not fixed.

 

Thanks again, xflat. I will do an av scan (avast) and an online scan (House Call) and see what's what. (I usually do this and other maintenance items) every Monday.)I've just been called away (Sunday evening with family), so it will be awhile before I get to this. But I WILL do it and let you know.

 

It's okay, don't know why

Well, xflat, I suppose you will understand this but I don't. I went through all the stuff on my list--avast, house call, ad-aware, spybot--and nothing wrong was found. Also did the regular ScanDist and Defrag. All okay. Finally, I got around to Ctrl+alt+delete and saw "msimn [not responding]" I thought that msimn had something to do with OE, so I clicked "End Task." When I next tried to open OE, it opened! And it has done so several times since then, so I guess things are okay. Thanks for all your interest and help. I have asked MajorGeeks numerous questions and I'm always impressed with how somebody generally comes up with an answer and/or good advice..