Unfortunately Lotus Notes hangs on my pc all the time with no apparent reason. It does look like it has issues with replicating databases, but the database that has problems can change and about 20% of the time it does actually work. The other 80% of the time is a pain as I am working offline, go to my mail and all the recent stuff is not there. Alternatively I go to shut down Notes and it fails because it gets stuck on trying to replicate. So my favourite tool at the moment is Zapnotes which does a good job of killing notes processes and restarting notes. Sometime though I get the error message “An error was encountered while opening a window” – this can be solved by clicking ok to close notes and then running (in my case) c:\program files\lotus\notes\nsd -kill
No need for a reboot.