I have the same issue, and increasing the maximum attachment size did NOT fix it. After that change to php.ini, I can COMPOSE A NEW EMAIL with an attachment of 5MB just fine, but if I open an email in my inbox with an attachment larger then 1.4MB and then click the "Forward" link, I will always without fail, get the "Page cannot be displayed" error page.

I am able to forward emails with small attachments with no problem.

I am running Squirrelmail on a Linux server, and I'm viewing the site via Windows XP. Anyone have this problem, or have any ideas?

I found a possible solution at http://www.ccil.org/help/squirrelmail.php
but the article mentions "Unfortunately, after adding this information, we've since heard that this change did not help several users who were getting this error message" which was my case as well.

HELP!