Same problem, immediately upon upgrading from bitcoin-0.8.0rc1-win32 to 0.8.1, on Win7-64.
Chose Cancel. The .sst file referenced did not exist, but no problem creating the .sst file with Cygwin "touch". Deleted the .sst file I had created, restarted Bitcoin-Qt, ran fine the second time, no further mention of .sst files in the debug.log. 2-month old SATA laptop drive with no problems.
Bitcoin version v0.8.1-beta (2013-03-17 15:35:36 -0400)
Using OpenSSL version OpenSSL 1.0.1c 10 May 2012
Startup time: 2013-03-20 12:52:37
Default data directory C:\Users\username\AppData\Roaming\Bitcoin
Used data directory C:\Users\username\AppData\Local\LargeDB\Bitcoin
Using 4 threads for script verification
init message: Verifying wallet integrity...
dbenv.open LogDir=C:\Users\username\AppData\Local\LargeDB\Bitcoin\database ErrorFile=C:\Users\username\AppData\Local\LargeDB\Bitcoin\db.log
Bound to [::]:8333
Bound to 0.0.0.0:8333
init message: Loading block index...
Opening LevelDB in C:\Users\username\AppData\Local\LargeDB\Bitcoin\blocks\index
Opened LevelDB successfully
Opening LevelDB in C:\Users\username\AppData\Local\LargeDB\Bitcoin\chainstate
Opened LevelDB successfully
LoadBlockIndex(): last block file = 14
LoadBlockIndex(): last block file: CBlockFileInfo(blocks=789, size=119258104, heights=225479..226267, time=2013-03-12..2013-03-17)
LoadBlockIndex(): transaction index disabled
LoadBlockIndex(): hashBestChain=00000000000002e60135b76ddd31d727f4ca44c28f142e85ff38c199b1a098e8 height=226267 date=2013-03-17 02:17:42
init message: Verifying block database integrity...
Verifying last 288 blocks at level 3
LevelDB read failure: IO error: C:\Users\username\AppData\Local\LargeDB\Bitcoin\chainstate\013292.sst: Could not create random access file.