Just wanted to add, this is also happening with ubuntu 6.06 (32bit) and unrealircd 3.2.3, using enc_none and no third party modules.
Core dumps are never generated from this, even though DumpCore is enabled in services.conf.
When a new channel is registered, a crash occurs immediately, and the newly registered channel is not saved in chan.db (so this crash can always be reproduced just by re-registering the exact same chan (or any other)).
Reverted back to 1.7.21 again and all is fine.