Before you copy the blk* files, you must run with the -detachdb option and make sure you shutdown bitcoin and wait for it to exit completely. With 0.6.2, we change the default from "take a long time to shut down, but leave standalone .dat files" to "shutdown quickly, but leave .dat files that are tied to the database/log.* files".
Too many ordinary users were quitting bitcoin and then immediately powering off their systems, leaving the database in a bad state.
Thanks for the info Gavin,
I followed these steps and now 0.6.3 is running fine on 64-bit Xubuntu 11.04.
Note 1: While waiting the 10 minutes or so to shutdown using the -detachdb option the GUI looks like it's not responding.
Note 2: Before I copied the blk* files, I needed ~1350 blocks to synchronize with the network but when I restarted 0.6.3 the count was only ~1050 blocks. After a couple of minutes, the count
increased to ~1225.
Note 3: I was only able to connect to 8 nodes on 0.6.3 even though the bitcoin.conf hasn't changed and I normally connect to +100 nodes.