Good morning,
We are a firm of approx 50 employees. We have a 5 user license for our BES server. Which is running on Windows 2003 server. This is the only role this server is performing.

Our primary server is running Windows 2008 and Exchange 2007. I am planning to perform updates and upgrade the ram over the weekend.

Understandibly the BES will not be able to communicate with Exchange for a short time period. Is there any thing I should prepare for. Will the BES be able to re-establish communication or will I need to restart services. etc etc.
Thank you.

you'll see lots of mapi connectivity errors and should reboot the BES after the maintenance is complete and Exchange is back online.

You may / may not have to restart depending on how MAPI reacts. I always recommend restarting BES after Exchange store maintenance.

Also, it may take a while for the BES to re-sync with Exchange. I have done similar maintenance on Exchange 2003 and even after restarting BES services, then rebooting BES, the BlackBerries were still not getting emails. After talking to BES tech support, they said with my 100 users to expect 2 to 3 hours for BES to re-sync with Exchange. They basically said to be patient and let it work itself through.