I am running XP on an Acer C110.
I can no longer use the tabtip.exe for screen entry, as it produces an error with two reports to Microsoft. The task is still running, but trying to bring up the input area does nothing. I can kill the task and try again, but get the errors again. The surrogate keyboard that appears at the Windows login screen still works, but not tabtip.exe.
This all started around the time frame of the July 10 MS updates, but doing a system restore back prior to that date did not help. I have had some problems with updating the .NET framework, but totally removing all versions of .NET framework did not help. However I have a gut feel that there is a connection. The .NET has now been reinstalled and everything is up to date.
Good thing that the computer has a real keyboard, but I really would like to be able to use it as a tablet. The pen does still work, but I can only use it for clicking since there is no area to write into.
I have a second Acer which has less software on it, and tabtip.exe works fine there.