I tried installing 14.04 LTS, 14.10 and 15.04 beta 1 in three virtual machines on top of my non-virtual 15.04 beta 1, patched all up to the most recent patches (last night) and all three showed no issue with MATE Menu.
Therefore I recommend that this defect should be closed. There might have been some transient issue day-to-day in the patching sequence which caused a problem.
I tried installing 14.04 LTS, 14.10 and 15.04 beta 1 in three virtual machines on top of my non-virtual 15.04 beta 1, patched all up to the most recent patches (last night) and all three showed no issue with MATE Menu.
Therefore I recommend that this defect should be closed. There might have been some transient issue day-to-day in the patching sequence which caused a problem.