Asterisk Real time configuration problem

Hi,
I am new user in Asterisk, I having a problem in Real time configuration.
I am working on fedora core 4, I installed asterisk, asterisk-addons,mysql 5 on the system.
I create the asterisk dateabase and also create the tables for users and extensions.
I also change the extconfig.conf and res_mysql.conf files but i am getting this error on CLI,

May 18 13:39:47 ERROR[2936]: res_config_mysql.c:615 mysql_reconnect: MySQL [color=red]RealTime: Failed to connect database server asterisk on 127.0.0.1. Check debug for more info.[/color]
Transmitting (no NAT) to 10.19.200.75:5060:
SIP/2.0 404 Not found
Via: SIP/2.0/UDP 10.19.200.75;branch=z9hG4bK2109f932f7fb9c7a;received=10.19.200.75
From: “grandstream1” sip:grandstream1@10.19.200.73;tag=1dca3d45eb66cb98
To: sip:grandstream1@10.19.200.73;tag=as0912463f
Call-ID: c94c21187844f700@10.19.200.75
CSeq: 4901 REGISTER
User-Agent: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Max-Forwards: 70
Contact: sip:grandstream1@10.19.200.73
Content-Length: 0


May 18 13:39:47 NOTICE[2936]: chan_sip.c:10824 handle_request_register: Registration from ‘sip:grandstream1@10.19.200.73’ failed for ‘10.19.200.75’ - Username/auth name mismatch
Scheduling destruction of call ‘c94c21187844f700@10.19.200.75’ in 15000 ms
Destroying call ‘81c39bd3d5832d93@10.19.200.77’

<-- SIP read from 10.19.200.77:5060:
REGISTER sip:10.19.200.73 SIP/2.0
Via: SIP/2.0/UDP 10.19.200.77;branch=z9hG4bK20a44a7c3da43187
From: “grandstream2” sip:grandstream2@10.19.200.73;tag=c3759d1a446813fe
To: sip:grandstream2@10.19.200.73
Contact: sip:grandstream2@10.19.200.77
Call-ID: 81c39bd3d5832d93@10.19.200.77
CSeq: 4902 REGISTER
Expires: 3600
User-Agent: Grandstream BT100 1.0.5.11
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0

before highlighted error, there was error mysql peers found but mysql engine unable to start…
Can any body help me solve this issue…thanx in advance
Faisal