I recently discovered that, during my September 2006 upgrade of Drupal, there was database corruption. I'm not certain exactly how it happened, although I am certain of the character sequence which caused it.
Basically, some posters on my site use "smart quotes" when posting comments. From my database dump of 2006-09, I can see full entries for certain comments and blogs. However, more recent dumps show every entry with a right-hand "smart quote" truncated just before the right-hand quote.
Here is my current plan. Note the lack of know-how in the final step:
1. Clear current database
2. Restore from the known-good September backup, and see if the corruption recurs. If it does, figure out a way to escape the backquotes during the import so that it's not corrupted.
3. Figure out a way to restore only that data which has been modified since September. This includes a number of blog entries where I have modified the entry due to changing circumstances, such as closing a controversial entry for further comment, adding a note to the top of a particularly popular entry, etc.