MySQL problem with vBulletin 1.1.5

[Bjoern]

I upgraded from version 1.1.2 to version 1.1.5, before this upgrade everything worked just fine, but now my database server does not accept connections anymore a few minutes after I restarted it, since obviously vBulletin opens a whole bunch of new processes every 10 to 30 seconds, though it should use persistent ones.

[Bjoern]

This is the error produced:

Warning: MySQL Connection Failed: Lost connection to MySQL server during query

And these are the mysqld settings:

[mysqld]
port = 3306
socket = /tmp/mysql.sock
skip-locking
set-variable = max_connections=5000
set-variable = key_buffer=512k
set-variable = long_query_time=5
set-variable = net_retry_count=120
set-variable = net_read_timeout=360
set-variable = join_buffer=25M
set-variable = max_allowed_packet=24M
set-variable = table_cache=15M
set-variable = sort_buffer=25M
set-variable = record_buffer=25M
set-variable = thread_cache=15M