Thanks Brian. As with most computer issues, a reboot seems to have done the trick. But I'll keep your advice in the back pocket for the next time this happens!

I recently installed the latest version of PMail onto my new laptop (Windows 7). I use it as a front end to manage my GMail. It's been working mostly ok. This evening, while not doing much other than reading through some older items still in my New Mail folder, I got the Windows pop-up "Pegasus Mail for Windows has stopped working. " with the options to "Check online for a solution" or "Close the program". Of course I chose "Close the program". Tried to re-open PMail, and got the usual "Mailbox is locked by another process" message which one always gets when PMail was not closed down properly. On choosing "Continue", I immediately got the same "stopped working" pop-up window. Left it for 10 minutes or so, tried again, same story. Tried several more times. Same story. I am thus unable to get into PMail.

I've looked at the directory and can't see anything in there that should be causing issues. I moved the three most recent .CNM files to a different directory, but that didn't help.

Move ALL of the .cnm files out of the mail directory and see if it will start up.  If it won't, rename the PMAIL.INI file to something like PMAIL_INI.BAD then attempt a startup.

If it starts up, most of the configuration settings will be at defaults.  You can try restoring a backed up PMAIL.INI file if you have a recent one otherwise manual reconfiguration will need to be done (I hope you only had one identity). 

Move the .cnm files back once things seem back to normal.