Parallels 11 notified me of an update last night, 7/31/16. I ran the update overnight but have logged in to my Macbook Pro this morning to find that Parallels was not running. It also seems to have erased my Windows data file in the Documents>Parallels folder. I have made no other changes besides starting this update.
Update - Found my PVM file in the trash bin. I did not delete it, so didn't think to look until now. Whew. (I also had a two-day old backup on an external drive but didn't want to lose anything if possible).
Almost the same thing has just happened to me. I was starting to do something else, Word for Windows was open and the Paralllel Desktop update window popped up. I decided to go ahead and install it before starting something new. I clicked on install, the program began removing the existing version and I left the room. About 40 minutes later I returned and the needle had not moved. I tried clicking it off to start again but the whole machine was hung and I could do nothing except manually restart. When I did this I found that the Parallel Desktop had apparently removed the old version but not installed the new version. The only option I can see is to try to just install the updated version as the other one is apparently gone. I cannot find it in trash. I can find the Windows 10 pvm but it doesn't react to anything. I don't want to do take any other complex steps that could cause the entire Mac Mini to crash and be unusable. I rely totally on the technician who installed the parallel system for me, but he is on vacation for another two weeks. I need my programs that only work on Windows, especially WORD ,the Thunderbird email program, my scanner that is installed under Windows and the Windows version of my Excel program from MS Office that is lnked to that of a company I work with.