I had some weird things with the Sonitus effects after installing 3.0, the plug in patch B, 3.1 and then 3.1.1.
Everything worked fine for new projects, but I lost the ability for recorded automation on my busses only.....
No-one else reproduced this directly but there are a few reports of weird automation issues floating around on a couple of forums.
Either way, the program is stable and the problem I experienced was fixed by copying tracks into a new file and project.
Q.
P.S. Did you find anything else out from Cakewalk on the summing thing?