Don't know about how to "check each OLE DB status value", but some probable issues:
1. You forgot to delete the searchcursor object, and locks persit on the table (that's why you can't update it).
or
2. Since your ODBC table (probably) doesn't have an OBJECTID field, the ESRI updatecursor method might not work. I know it used to be in v9.3 that your couldn't use the cursor sort parameter (in a search or update cursor) unless there was an OBJECTID field. You could always make your table drink the ESRI-brand coolaid and import it using CopyRows or TableToTable or some other tool - thus auto creating an OBJECTID field...