Bitcoin-Qt version 0.8.5 is now available from: http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.8.5/
This is a maintenance release to fix a critical bug; we urge all users to upgrade.
Please report bugs using the issue tracker at github: https://github.com/bitcoin/bitcoin/issues
How to Upgrade
If you are running an older version, shut it down. Wait until it has completely shut down (which might take a few minutes for older versions), then run the installer (on Windows) or just copy over /Applications/Bitcoin-Qt (on Mac) or bitcoind/bitcoin-qt (on Linux).
If you are upgrading from version 0.7.2 or earlier, the first time you run 0.8.5 your blockchain files will be re-indexed, which will take anywhere from 30 minutes to several hours, depending on the speed of your machine.
0.8.5 Release notes
Transactions with version numbers larger than 0x7fffffff were incorrectly being relayed and included in blocks.
Blocks containing transactions with version numbers larger than 0x7fffffff caused the code that checks for LevelDB database inconsistencies at startup to erroneously report database corruption and suggest that you reindex your database.
This release also contains a non-critical fix to the code that enforces BIP 34 (block height in the coinbase transaction).
Thanks to Gregory Maxwell and Pieter Wuille for quickly identifying and fixing the transaction version number bug.