Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies
  Warning ! ! This will log you out of sites you're logged in to.

Type about:preferences<Enter> in the address bar.

• Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
• Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

I thought it had cracked the problem - all OK having switched off hardware accelleration in safe mode..... but, when I restarted Firefox, Google calendar froze again.....

Same problem, refreshed Firefox and then Calendar OK but this morning, frozen again. Refreshed again and OK but have to reset search page each time and WHY does it keep happening. Have booked onto the Google Calendar support, gave refresh details but now its at it again. Also it does not seem to sync to mobile but this is secondary problem. Is Firefox looking into this?

A post was flagged as Solved Problem. Please remove that flag. If you don’t, others that can help may not read this post.

The problem is fixed until you restart Firefox.

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

I refreshed Firefox and that seems to have fixed the problem - thank you for your time.

That was very good work. Well Done.

Mmmh - same problem a few days later.....

Retry all of the above. I've called the big guys to help you. Good luck.

A post was flagged as Solved Problem. Please remove that flag. If you don’t, others that can help may not read this post.

Go to that message, and use the link to it's right.

This is not solved but do know how unflag it - only report abuse is on right.

I'm still having this problem on a regular basis.....

I too am still having same problem. Have reported it to Google and to Firefox/Mozilla so have now decided to use the Yahoo calendar. Not worked out how to sync to mobile phone yet but as the Google Cal was not working on new mobile anyway I can wait.

I have had this problem now almost a month too....refreshing firefox helps only for a moments. Using windows 7 and firefox 46.0