Recovery isn't hard; just delete the .bitcoin/database/log.000* file(s) and any .bitcoin/__db*.log files. Were you previously running a self-compiled version of Bitcoin?
From http://subversion.apache.org/faq.html#divining-bdb-version :
Code:
cd ~/.bitcoin/database
od -j12 -N8 -tx4 log.000*
od -j12 -N8 -tx4 log.000*
... will show what version of BDB the log files were written with.