When activating email scanning in Comodo Antivirus Thunderbird loses all my email accounts passwords and when it askes for them it can never authenticate with the email server (keeps asking for the password). When deactivating email scan everythings fine!?
This is a known bug in CAVS and is being worked on for the next version (CAVS 2.0) due October 14th. As a workaround, it works if you manually check each mail account, rather than having Firefox check all on startup.
Pain in the proverbial, I know (I’ve got the same issue), but hopefully we’ll only have to wait until the 14th.