THIS IS VERY BAD. WE ALL KNOW THAT MAKING DIRECT UPDATES TO THE DATABASE WILL CREATE SOME SORT OF BLACK HOLE AND KITTENS DIE IN REDMOND ETC, ETC. I HAVEN'T TESTED THE LONG TERM EFFECTS AND ONLY DID THIS ON MY DEVELOPMENT ENVIRONMENT TO GET ME OUT OF A PICKLE.
If you ever get this error when trying to update a field, either through the web UI or programmatic-ally it normally means your Version fields are out of sync. This can occur if your field has been created using the Schema XML from another environment or you have migrated content using some dodgy 3rd party app.
Run this update on your content databases and you all should be good again.
SET [Version] = CAST([Definition] AS XML).value('(/Field/@Version)', 'int')
WHERE CAST([Definition] AS XML).value('(/Field/@Version)', 'int') <> [Version]