In Squirrel mail I set the number of emails per page to 100. I clicked toggle all. I clicked Archive. it goes to a white screen and does not come out of it. I lowered the number of emails per page all the way down to 2 and it still went to the white page. I tried this on multiple emails multiple computers and Chrome and Firefox.
What OS are you running on those computers? I am running Windows 7 and e-mails will archive just fine.
-Blackmage