070110 11:07:00  InnoDB: Started; log sequence number 309 1786458775
070110 11:07:00 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=portland-relay-bin' to avoid this problem.
070110 11:07:00 [Note] Slave SQL thread initialized, starting replication in log 'nepal-bin.000193' at position 1240, relay log './portland-relay-bin.000386' position: 1377
070110 11:07:00 [Note] /usr/local/sbin/mysqld: ready for connections.
Version: '5.0.26-standard-log'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Edition - Standard (GPL)
070110 11:07:00 [Note] Slave I/O thread: connected to master 'repl@nepal:3306',  replication started in log 'nepal-bin.000193' at position 1240
070110 11:18:29 [Note] Slave I/O thread killed while reading event
070110 11:18:29 [Note] Slave I/O thread exiting, read up to log 'nepal-bin.000193', position 481236676
070110 11:18:29 [Note] Slave SQL thread exiting, replication stopped in log 'nepal-bin.000193' at position 218341976
070110 11:19:46 [Note] Slave SQL thread initialized, starting replication in log 'nepal-bin.000193' at position 218341976, relay log './portland-relay-bin.000388' position: 218340971
070110 11:19:46 [Note] Slave I/O thread: connected to master 'repl@nepal:3306',  replication started in log 'nepal-bin.000193' at position 481236676
mysqld got signal 11;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help diagnose
the problem, but since we have already crashed, something is definitely wrong
and this may fail.

key_buffer_size=134217728
read_buffer_size=1044480
max_used_connections=4
max_connections=120
threads_connected=4
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_connections = 376351 K
bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

thd=0x96080e8
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
Cannot determine thread, fp=0xbf91e958, backtrace may not be correct.
Stack range sanity check OK, backtrace follows:
0x80a0a12
0x82fb4e8
0x82f999b
0x833689a
0x82b0696
0x82b0d8c
0x81020f1
0x81021b4
0x810235b
0x8088b0a
0x808a968
0x81513e2
0x81509d0
0x80b4b89
0x80b944a
0x8111059
0x8115453
0x816cac9
0x816d91b
0x82f8c9c
0x83412ea
New value of fp=(nil) failed sanity check, terminating stack trace!
Please read http://dev.mysql.com/doc/mysql/en/Using_stack_trace.html and follow instructions on how to resolve the stack trace. Resolved
stack trace is much more helpful in diagnosing the problem, so please do 
resolve it
Trying to get some variables.
Some pointers may be invalid and cause the dump to abort...
thd->query at 0x96f4d00 = *** Please see private comment to view query text ***
The manual page at http://www.mysql.com/doc/en/Crashing.html contains
information that should help you find out what is causing the crash.