Comment 12 for bug 908531

Let me provide feedback.

Between 5.1.59 and 5.1.60 changed memory allocation in the mysql:

diff -ruN mysql-5.1.59/sql/sql_cache.cc mysql-5.1.60/sql/sql_cache.cc
--- mysql-5.1.59/sql/sql_cache.cc 2011-08-11 22:52:53.000000000 +0900
+++ mysql-5.1.60/sql/sql_cache.cc 2011-10-30 03:09:47.000000000 +0900
@@ -1251,7 +1251,7 @@
       DBUG_PRINT("qcache", ("No active database"));
     }
     tot_length= thd->query_length() + thd->db_length + 1 +
- QUERY_CACHE_FLAGS_SIZE;
+ sizeof(size_t) + QUERY_CACHE_FLAGS_SIZE;
     /*
       We should only copy structure (don't use it location directly)
       because of alignment issue

My fix https://code.launchpad.net/~tsarev/percona-server/5.1_fix_bug_856404/+merge/87203 of bug #924872 include changes related to this feature.
Unfortunatelly, this fix not merged to 5.1.60 :( This is a reason of your crash.