Here's an example error message that might prevent bitcoind/bitcoin-qt from starting: EXCEPTION: 22DbRunRecoveryExveption DbEnv::open: DB_RUNRECOVERY: Fatal error, run database recovery C:\users\omistaja\paska\bitcoin..... in Runaway exception
This message is what end users can easily find and relay when confronted with their wallet not starting. Currently it's very uninformative. It basically just says "there is a problem with the database". It should be fixed so it actually gives some details on the problem. For example what database file is causing the problem.
Also, I don't know if that's already being done but the less important database files could just be wiped automatically when this happens so the software can at least start.