I am having the same issue, and I tried different combinations for file type. The best result I got is when I put *.slddrw as file type, but it only changed the top level file.
Another strange behavior is that variable where I set the value to <%user%> will disappear when I open the file.
Hi Alex, thanks for the reply, it seems that the issue you have is more complicated when it works in some cases but not works in other cases.
The issue I have is PDM with SP4, PDM with SP3 is actually working well, but it doesn't work with SP4 completely.
I have got feedback from our VAR and solidworks released a hotfix, and it is working now.
You may check with your VAR and get this hotfix from solidworks, hopefully it helps you solve the issue.