I've been having some problems with my template not saving under Expand Widget Templates in blogger, instead I receive a full page error message. I can save when Expand Widget Templates is un-checked.
I've realized the problem is I've added some code to my template that blogger can't save, or produces an error page.
For me the main problem was the Google Analytics code I added to my template, once I removed it everything worked perfectly.
So if your having this same problem, you may want to check out the codes, widgets etc that you've added to your template, the solution may be as simple as a few lines of code.