I believe I saw something similar during Beta. The actual problem was that opening a new assigned item by somebody with view only access, the automatic build-in logic tried to set the assignment status to accepted.
If the item assignment status is allready on accepted and you still get the message, you will have an other problem.
I hope this bring you 1 step closure to find the actual root cause.
We are also suffering from this. We have logged a call with HP, and have been told that this is related to a bug, where when you only have read rights somehow the program behaves strange. If i remember right they believe this is fixed in SP1. I somehow have my doubts.
The original bug we report was that when you only have new and view rights to the history, which is what our users have. The Registration information of a history entry only displays correctly on the overview tab. When you open a history entry.(you get first the annoying error message you described) and then the registration information is either blank or it displays your own information. When you give the users modify rights it is displayed ok
Hope you get what I'm trying to explain ;-)
So HP told us both problems are related to each other. Hope it is true.
Well, the role which has only read only permision, can those users access SD thru a browser? Will that reoslve ? Or, create a custom filed, give read & write access for the role. Then, fill the field with a messge saying all the fileds are read only, user can;t make any chagnes.
May be this is a dirty thing, but i hope it will not give u the annoying message.
There is a workaround, you grant your users the 'Modify' access right in that role, but under 'Advanced' for a desired object, you change the Access for ALL the attributes from Write into View, I did it like this and it works just fine.