mysqld-nt.exe: Out of memory

Once a day, any query that uses "COUNT()" stops working and I get an error like this:
C:\Program Files (x86)\Parallels\Plesk\Databases\MySQL\bin\mysqld-nt.exe: Out of memory (Needed 8382496 bytes)

So I usually have to restart the MySQL service to fix it.  I realize that it's probably the mysqld-nt.exe process using up to much RAM.

Basically I need help on modifying my my.ini file so that it uses up a little less RAM.  Here it is:
 

[MySQLD]
port=3306
basedir=C:\\Program Files (x86)\\Parallels\\Plesk\\Databases\\MySQL
datadir=C:\\Program Files (x86)\\Parallels\\Plesk\\Databases\\MySQL\\Data
default-character-set=latin1
default-storage-engine=MYISAM
innodb_additional_mem_pool_size=2M
innodb_flush_log_at_trx_commit=1
innodb_log_buffer_size=1M
innodb_buffer_pool_size=16M
innodb_log_file_size=10M
innodb_thread_concurrency=8
max_connections=9000
old_passwords=1
max_user_connections=9000
max_connect_errors=1007
thread_cache_size=512
thread_stack=196608
binlog_cache_size=4M
net_read_timeout=30
net_retry_count=10
net_write_timeout=30
thread_concurrency=8
open_files_limit=0

# This Caches Select Queries
query_cache_size=128M
query_cache_limit=16M

# Added by AccuPro to log slow queries
log-slow-queries=C:\Program Files (x86)\Parallels\Plesk\Databases\MySQL\slow-log.txt
# More added by David
#log-queries-not-using-indexes
long_query_time = 3
#log_long_format

#*** MyISAM Specific options
# Modified by AccuPro myisam_max_sort_file_size from 100G to 5G
myisam_max_sort_file_size=10G
# Modified by AccuPro myisam_sort_buffer_size by AccuPro from 8M to 256M
myisam_sort_buffer_size=256M
# Modified by AccuPro read_buffer_size from 64K to 8M
read_buffer_size=8M
# Modified by AccuPro read_buffer_size from 256K to 8M
read_rnd_buffer_size=8M

# Added by David
max_allowed_packet = 16M
join_buffer=4M

max_heap_table_size=256M
tmp_table_size=256M

record_buffer=8M


# Modified by David
key_buffer_size=512M
table_cache=2048M
sort_buffer_size=4M

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Keep in mind that the entire purpose of this server is to be a Database server, it's got no other purpose.  It's a pretty powerful server to, here's the specs:
-OS: Windows 2008 64-bit Std. Edition
-CPU: Intel Core 2 Quad - 2.83 GHz
-RAM: 4 GB
-Plesk Control Panel