Hi All,
Thanks for the suggestions. Just trying to button this up. No "solution" was found, although there are some workarounds and untried suggestions. The problem seems to be isolated to projectwise files.
Workarounds:
Using the double down arrows to the right always works.
Right clicking on any layout tab and selecting "activate model tab" always works.
If I open autocad and use file>open to browse to the file (rather than just double clicking a file in projectwise), model tab appears.
If I open a drawing by double clicking in projectwise, no model tab. If I open a second drawing by same method, model tab appears in both drawings.
Untried suggestions:
Install latest service packs, potentially SP4. I'm on SP1, but so are the rest of my colleagues - working for a big company, I can't go rogue and install a newer SP than everyone else.
Thanks everyone!