Strange Thunderbird IMAP problem

[John Thompson]

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I have 2 computers here running linux and using Thunderbird for email.
One is a laptop, running Vectorlinux-4.2; the other is a desktop,
running Fedora 10 x86_64. Thunderbird is configured identically on both
to ccess to separate IMAP accounts. Until this morning, both worked
fine. Now the Fedora machine can no longer access my gmail IMAP account;
it times out without establishing the connection. My laptop can still
connect perfectly well. Did I mention they were configured identically?
There are no firewall rules blocking gmail on the desktop machine:

[root at lancre ~]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain blocksshd (0 references)
target     prot opt source               destination

I can send mail from the desktop machine via gmail's smtp service, but
copying the sent message to the IMAP folder fails, because the
connection cannot be established. The mail is received properly by the
laptop machine.

WTF is going on? The only change in the system was installing Fedora's
newest kernel and rebooting, as requested by the system update applet.

# uname -a
Linux lancre 2.6.27.19-170.2.35.fc10.x86_64 #1 SMP Mon Feb 23 13:00:23
EST 2009 x86_64 x86_64 x86_64 GNU/Linux

The last mail received from gmail on the desktop machine was at 0745CST
this morning, just prior to installing the new kernel and rebooting.

I can't imagine a kernel update specifically blocking IMAP on gmail, but
I have no other clues to go on.

- --

John (john at os2.dhs.org)

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