Thunderbird doesn't normally do that. I don't think there is a fault in Thunderbird causing what you describe.

Perhaps your profile has been placed in some location where you don't have write permission, so whatever you do can't be written to disk. Or your profile folders and files have been made "read only".

Thank you for your help I've tried everything I can. I know I am not very good at sorting problems I am really a newbie to Mozilla and like it but I think I am going to give it up its started losing my passwords now

But thank you for your help

Do you use anything like CCleaner ?

Do you use 'Avast' anti-virus software ? Is Thunderbird set to run in Avast's Sandbox? This could cause the issue you are experiencing as everything is virtualised.

check to see if the Thunderbird icon Properties has it running in Sandbox?

Lockman said

I set up Thunderbird with my email accounts and it works fine. but now it has started to lose the accounts and information even the address book when I log out. all gone. I have to set up all the accounts and address book again when I start Thunderbird The program works alright and it collects the email alright, but shut it down and all information has gone again.

Thank you all for your help especially Toad Hall I followed your instructions, not quite sure what I did but it seems to be Ok now keeps my information and it even retrived my address book