You should NOT turn off the prompt to save changes to the normal template.
See Do you want to save changes to the template? Keeps popping up!
The problem is with saving changes to normal.dotm. If this is the problem, you probably also can't save changes to your default font or styles.
The usual block to saving the normal template is a poorly written Add-In. Try disabling all your Add-Ins using the two buttons on the Developer Tab. The Add-In that seems to have been causing the most trouble lately has been one to assist with Blue-Tooth. If you find that disabling all your Add-ins lets you save your AutoText, then go through disabling them one at a time until you find the one that is causing this. Once you do, decide whether you really need it; if you do need it, contact whoever wrote it and complain.
When something this strange happens my first suspect is one or more poorly-written Add-Ins, which you may not even know you have.
Try closing Word and starting it without Add-Ins. To do this, find the Run command under the Start Menu and copy the following line into the box, press Enter.
winword.exe /a
If this temporarily fixes your problem, write back and we'll talk about Add-Ins.