Are there any differences here between the two systems? I see you've posted FMP 8.0/8.5. Is one site 8.0 and the other 8.5?
I don't have either version, but when I drag and drop into a container in filemaker 11, I get the equivalent of Insert Object and it appears to work. I can add the file to the container and double-clicking opens it in the native application.
Perhaps a simple test may reveal something. On the system where it doesn't work, create a brand new file with just a container field and see if you get the same results when you drag and drop into this container field. If you can't drag and drop into that field, then you've ruled out issues with the file itself.
The site that does not work is 8.5. I created the new FMP file with only a container field and the results are the same.
When I dragged and dropped the file onto the container, it gave me the following error:
I was able to right click and insert the file into the container with no error. However, when I double-clicked the file, it still did nothing.
I wish I had copies of 8.0 and 8.5 to test, but I don't.
Right-clicking probably is doing a different insert such as insert "picture" or "file" instead of "object". You may be able to use Export field contents in the edit menu to open the inserted file. This can be scripted and the script can specify the temporary items folder so that no "clutter" is created on the computer--though you'd have to re-insert the file after changes are made.
I've discovered that as an option. I'm not sure I trust our users to get their file re-inserted after the edits are made. I was just hoping I had missed an option box someplace in my install or field creation process or something.
One last effort:I went to the machine running the Filemaker server and it wouldn't let me drag and drop a file into the container either. I used the "insert" command, but when I double-clicked it, it wouldn't open.Just an FYI, it works on a Mac. I used an Excel file I had on my desktop as a test, and it let me drag and drop it in the container, and open it.This has to be a Windows issue...right?