In here, we have installed the cumulative patch 2 and from there, we had issue with user in approval group but who are not able to open the request.
We found that since CP2, the user with a role "Catalog User", even if he is in the approval group, are not able to look at the request.
We had to change all role of the approval user to "Request manager". Seems that they have changed something.
It could be your problem here.. Maybe.