The AdvanceCache.get() method is not thread-safe which could be the cause of
this problem althouyh absent a test case its hard to say for sure, or
even to test a fix.
The observed code problem is that it synchronises entry to a block on
a variable "cache", but inside that block assigns a new object to "cache"
so 2 threads can enter, one on each variable and be accessing state variables
which are not meant for simultaneous access
This isn't a problem in 1.5 as the cache is disabled and we probably
could just delete the class ..
If a 1.4.X fix is needed probably the easiest thing is to chose a new
object on which to synchronise.