Your google approach was correct: http://drupal.org/node/529866 has a good rundown on this.

I've also had major serialization issues with simplexml. In that case you have to store XML into the cache after converting to xml using simplexml's methodology - you can't just dump a tree into the drupal cache.

-Randy

On Tue, Dec 1, 2009 at 2:42 PM, Jeff Greenberg <jeff@ayendesigns.com> wrote:
I asked about this at #drupal-support, and am waiting for an answer, but when I Googled it (+unserialize +"Error at offset" +"bootstrap.inc") I received 220,000 postings, so maybe this is a big issue I missed?  Unserialize error at offset x of y bytes in boostrap.inc?




--
Randy Fay
Drupal Development, troubleshooting, and debugging
randy@randyfay.com
+1  970.462.7450