Have a look at...

https://support.mozilla.org/en-US/kb/Backing%20up%20your%20information#w_locate-your-profile-folder

See also:

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

I followed the instructions. Closed firefox. Located old 'profiles' folder and 'ctrl' copied it. Then went to my _Library_ApplicationSupport_Firefox_Profiles and replaced the profile folder with copied one by 'Ctrl' paste item.

Went to open my firefox and this window showed up " Close Firefox - A copy of Firefox is already open. Only one copy of Firefox can be open at a time."

However, nowhere on my computer does it show that I have Firefox open! Once I copied and pasted 'old' profiles folder over the current, this is on. Now I cannot open Firefox unless I reverse everything. Any thoughts on that. Thank you.

See:

• https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding
• http://kb.mozillazine.org/Profile_in_use

See how you go with Cor-el solution... Have you tried a system restore to before the problems occurred?