Mysql Connections Topping Out Within Seconds

i have a small cluster (one web and one db) setup and i host a rather popular group of 4-5 sites that allow users to dynamicly create their own mobile chat communitys automaticly. each site gets its own mysql db created and populated automaticly.

this is all fine,

but in the last 24hours weird things have begun happening, previously i had the sql max_connections set to 500 and this was perfectly adquate for the demand but now even when i set the connection to 4000+ they are all maxxed out within 5-10 minutes, and mysql processlist shows thousands of unauthenticated user connections sitting at login status,

i have gone through the sites and all their mysql configs are fine so i cant see what the issue is.

server specs below

db server:
dual amd opteron 246
8GB ram
120gb hd(64gb free)
33gb swap (rarly used but their for emergencys)
centos 5 64bit.
direct 100mbit lan to web serv
only mysql,ssh and webmin running, no other apps installed

web server:
amd athlon 64 3800+
plesk 9.2.1
4gb ram
2x120gb hds

apache status onthe web server only shows 120ish http connections but the sql keeps climbing