Check out this thread viewtopic.php?f=1&t=66027. Developers at Mozilla are working on correcting this issue. Though they have had a pretty hard time reproducing it on their end. Try these steps to isolate the issue a bit further.
When the issue occurs, can you open your web console to see if this error appears :
"Corrupt structured clone data detected in IndexedDB. Failing the database request. Bug 1519859 will address this problem."
To open the Web Console:
either select "Web Console" from the Web Developer submenu in the Firefox Menu (or Tools menu if you display the menu bar or are on Mac OS X)
or press the CtrlShiftK(CommandOptionKon OS X) keyboard shortcut.
we'll sure this information with the Mozilla development team so they can continue to work on a resolution. Thanks so much for your help!
ABP Support Team