I can confirm this bug still exists, in Evolution 184.108.40.206 running on KDE 3.5.10 (basically Kubuntu 8.04)
There are some important points which the other bug reporters didnt mention. Heres my setup (and the accounts are checked in this order)...
2 gmail POP accounts
2 virgin.net POP accounts
Evolution will occasionally act as though gmail authentication has failed. I dont know whether this is really a fault on GMails servers, or a bug in Evolution, but I've never had this problem with any other email client using the same setup of accounts, and same frequency of checking
There is a definite bug in Evolution though, in that whenever gmail authentication appears to fail, both of my Virgin.net accounts start prompting for a password too. At this point even though the passwords entered are correct, the virgin.net password prompts will repeatedly appear until Cancel is clicked.
As with the other users, at this point if I click Send and Receive, all 4 email accounts authenticate correctly, which is why I dont think its a problem with GMail servers at all.
Crucially, this only ever happens when the email accounts are being checked automatically (ie, every 5 minutes.).
I have never had this problem after manually clicking Send / Receive