When setting a Redstone Port on the reactor, it sometimes throws an error of:

java.lang.ClassCastException: TileMultipart_cmp$$23 cannot be cast to erogenousbeef.bigreactors.common.interfaces.IReactorTickable

http://pastebin.com/1aE1ykHL

I can't seem to replicate on SSP, and upon re-loading the server everything works fine.

Weird. Can you paste the full exception? There's nothing called "TileMultipart" in BR, so I'm wondering if there's some odd incompatibility somewhere.

Specifically, I'm looking for the list of installed mods at the end of the crash.

You should see some log lines appearing when this error occurs now, instead of crashes. Please let me know what you find at the buggy locations so I can properly fix this.