I have tried many times to reset Messages app on Mountain Lion by deleting the plist files and cache. Regardless it always stops working again after a few days. Messages show up in the notification centre but when I clock them or try to open Messages the window does not show. After a restart I might be able to get the window to finally open only to see an empty window. The conversations seems to be in the left row, because when I click in the empty left space conversations show up to the right. They seem hidden. It just seems broken somehow.
Any thoughts on this?