Just recently, Thunderbird has failed to show me my incoming emails. It allows me to send mail, though not to save a copy of sent mail, which is a nuisance. It says it didn't save because errors occurred while running message filters, which is meaningless to me. It will save local copies. I reloaded Firefox, reloaded it in Safe mode, restarted my PC and as a last resort, reinstalled Thunderbird. All that seems to have happened is that the Windows 'processing' icon runs continuously when T'bird is loaded, including overnight. I use Eset NOD32 antivirus which I am told is one of the best. It has not reported any issues lately. Is this a known problem, and more importantly how do I fix it?