Try deleting the PGO files from both the root of the User Documents directory and the C:\ProgramData\QlikTech\Qvs folder (that's where the CALs are encrypted). Then restart the Server and Mgmt services. That should recreate a clean copy of the PGO files, which should hopefully get rid of the corruption.
Today, I noticed the exact same issue. Now we know how to get rid of it (Thanks Vlad!) but I would like to know what caused it. In my case, it is only one user, and it is quite a unique user (It is the one we use for test purposes and is also de Administrator account).
This user is the only one accessing via the iPad client, could it be related?
We use also the iPhone Client with this user, but there are others as well using the iPhone. I don't know what else is different for this user, so... Could you share with me the particularities of the users that presented the issue for you?