Thank you for your post, and I apologize for the late reply.
This error message usually occurs if the updater is already installed. Please launch FileMaker Pro, pull down the Help menu and select About FileMaker Pro. See if it displays 11.0v2. If it still displays 11.0v1, then make sure you are using the correct updater. That is, make sure you are not using the FileMaker Pro Advanced updater on the FileMaker Pro application, or vice versa.
I know some time has passed, and another updater (11.0v3) has been released. If you have found a solution, please post here so others who encounter this same problem may benefit from your experience.
We also got this error when we moved the (11.0v3) updater file from the folder into which it was downloaded. Specifically, we downloaded the file into our "Downloads" folder, then moved it onto the desktop and ran it. I can't remember why we tried moving the updater back into the Downloads folder, but when we did, the installation proceeded normally.