Indy, I think you are pointing us in the right direction. As I think about it, the situation changes when there is a change in the default program the OS uses to open the document. So my latest problem began when I tried to switch to Open Office on one of our machines. When I made that the default program to open Word files, it became clear that those files would not open in AC. (This is consistent with what you describe; a non-M$ program). When I changed the default back, though, the problem was not corrected.
I think the same thing occurred previously when my "trial version" of Office was called upon to open a document that was emailed to me. That changed the default for opening some Word and Excel files, and I lost the ability to open those files in AC. I managed to get it back, but now it is gone again with the Open Office issue.
Default is now set back to the earlier Word and Excel versions (2003) that worked before, but the behavior is the same.
Any suggestions?
My guess is that there is an internal setting in AC as to whether or not the machine it is running on has a M$ app on it, or the file needs to be passed to the OS to have the OS attempt to open it. Probably once set (or updated via a message from the OS), it doesn't seem like it looks again.
Sounds like one more question to ask AC support, which is how do we re-set that flag/variable, or point it to the correct third-party app to call.
If it is in a config file in say XML, easy enough to find it and change it; most of the folks on the board could knock that out in minutes.
