SOFTWARE VERSION:
3.2010.02-8.002

EXACT STEPS LEADING TO PROBLEM: 
1. Use N900 as usual
2. Suddenly, cellular network is not connected
3. Cannot regain connection to cellular network until reboot

EXPECTED OUTCOME:
Cellular network should work when there is a signal

ACTUAL OUTCOME:
Cellular network does not work despite there being a signal

REPRODUCIBILITY:
Cannot reproduce on demand. It has happened only once in over 5 months of
everyday use so far. 

EXTRA SOFTWARE INSTALLED:
2G/3G mode switcher

OTHER COMMENTS:
Today my N900 lost cellular signal. This normally happens tens of times every
day (maybe that is related to bug 9238 or just poor network coverage), but
usually it only lasts for a few seconds up to a couple minutes. This time it
lasted for more than an hour until I gave up waiting and rebooted. All the
while, other users on same network sitting around me had no issues with their
phones (not N900s). 

I tried to change the phone to off-line mode and then back to normal, but it
didn't help. I tried using 2G/3G mode switching applet to change between modes,
but that didn't help either. I went to Settings -> Phone, set network to Manual
(which normally lists available networks) and no networks were listed. I could
still access SIM card contacts, so I don't think the SIM card became dislodged.
Additionally and finally, I rebooted and cellular again worked normally when
the phone started up, with 5 bars 3G signal.

dmesg did not show any related messages during the "dead time", as far as I
could see.

If there is additional info that would help to debug this, let me know what it
is and I'll try it if this problem happens again.