Looks like something got caught in an infinite loop somehow. Reminds me of how BuildCraft power pipes (used to?) make the server blow up when you connect them in a loop, but this seems to be RedPower, or at least redstone, related.
Any additional info on what happened before the crash?
Not sure of the state of the server or the map, but if you have any idea of what might be causing it, you might want to back up the map and iteratively use e.g. MCEdit to replace certain blocks with air and see if the problem still persists. When the problem block type have been identified, see what you can do to minimize the impact when applying a fix on the backup map.