Have you reset the preferences as mentioned above? Here are the steps:
Reset your preferences to defaults.
1. Close PSE.
2. Start PSE on welcome screen and click Edit + immediately press and hold Control - Shift - Alt. If you get the keys down quickly enough - and you have to be very quick - PSE will prompt you to confirm deletion of your current preferences.
3. Confirm the deletion and PSE will start up with default preferences.
Found one of the solutions from forum posts. Please try
Switch the visibility of all the layers off. When you have a bunch of invisible layers, the file can be safely saved. Just do a copy, switch the layers off, save that copy and try it to reopen. If all is OK, switch desired layers on and now you should be able to save the file nomally.