Problem: Thunderbird hangs up on Macbook and iMac. It opens to the normal view, but if I try to do anything, I get the beachball of death. I used Mac migration assistant to install from Macbook to iMac. Before the installation, the Macbook Thunderbird worked fine, but after the installation, neither worked. My PC installation works fine, as does Apple Mail on my iOS devices, so it is not a provider problem. Solutions tried: restarting in troubleshoot mode, restarting iMac, turning off access to Apple Contacts, turning off antivirus (Norton), creating new profile and copying existing mail data into the profile folder, and renaming various files in the profile folder. Results: None of the solutions I tried provided access to my email. I can open the new profile, but that requires that I reenter all my email account information and copy the emails for each account into the new profile (I use POP). The problem may be with the prefs.js file, since if I rename it, Thunderbird doesn't hang, but would require me to reenter all my account info as if it were a new profile, and all preferences would be lost. Question: What is the best solution for this problem? Is there anything that would work better than reentering the account info -- e.g., can I make any changes to prefs.js using a text editor or some other utility?