Trouble with my icloud email

[MKing]

Had a Mac that " bought the farm". Switched my icloud acct. over to PC, not a problem in the world 'til I installed AVAST! Now I read a few emails, freezes-up, reboot and do the same thing over & over & over again. Much appreciate any thoughts on squaring away this P.E.T.A.  Thanks, MKing

[SafeSurf]

What version of Mac are you using and is it up to date?  There have been some updates lately.

What version and product of Avast are you using, and do you have or have you had any other security software on the machine?  If so how did you remove it? 

Are you having the problem using only one browser (Safari) or have you tried a different browser and duplicated the issue?

Are you getting your mail through the Dock Mac Mail (the icon with the Stamp) or though the browser webmail or another way?

Do you sync your PC with another device?  If so, are you having the issue with that other device as well that doesn't have Avast on it?