Contribution edit - "Could not find a valid session key" again

If you try to view and edit a contribution at the same time, you run into this error (see attached screen shot).

To reproduce, just:
1. go to a contact view
2. show the contribution summary tab (with at least one contribution)
3. open the contribution's 'edit' and 'view' screens in a new tab each in quick succession
4. observe the described error in the 'edit' screen

I observed this on the current 4.4.6 as well as on 4.5. I tried different browsers and cookie settings, but to no avail.

We also have the suspicion that this concurrency issue could erase the contribution's status - however, we were unable to reliably reproduce it yet.

This particular error message has been seen in a lot of tickets (just search "Could not find a valid session key"), but none seems to cover this particular problem.