Have file reserved w/ password but still get "locked for editing" dialog box when opening

Subject says it all. I have an excel file reserved/locked with a password that ONLY myself has access to. Sometimes when I try to open the file, I still get the "locked for editing" message b/c someone has it open, even though they must've opened it in read only format. I end up having to track down the culprit and have them close the file so I can get it. Any thoughts on this? Much appreciated.

Update: this morning, one of my people said he opened the file and "didn't think" it prompted him at all for password or read only and it opened right up. He wasn't completely sure about it but said he "thought" that was the case.

Originally Posted by TMS

Make him show you. If he can get in without a password, etc., others probably can too, and the file may not be locked as you think it is.

We tried and couldn't repeat the issue. So you're basically saying that password protecting the workbook only works sometimes. That's great. Sort of eliminates the point.