Unable to login more than 50 users

[heartzzzzz]

I have a clustered setup of Vicibox 4.0.1, Mysql is residing on server 2.
Server load on both the servers are minimal as not more than 60 concurrent calls are placed at anytime (2 Port Digium PRIcard configured on server 1)

Also Vtiger 6.0.0 is hosted on Server 1 & database is residing on Server 2 (similar to vicibox setup).

Everything is alright till the time number of users logged on vicibox is 48-50 users (Server 1), as soon as i try to login more than 50 users the web server gives up...
The web pages (Both Vicibox & Vtiger) doesn't load or takes ages to load and at the same time asterisk also slows down (Ratio 1:1, 20 Agents waiting for call & asterisk only dials out 2-3 calls). Logging out those additional agents brings back everything to normal.

What could be wrong? Im going nuts... Please Help.

Specs:
Server 1 (Asterisk & Apache)
ViciBox.i686-4.0.1
IBM-X3100-m4
NTEL XEON QUAD CORE PROCESSOR 2.4 GHZ OR 3 GHZ
HDD 1 TB
RAM 8 GB
Digium, Inc. Wildcard TE220 dual-span T1/E1/J1 card 3.3V (PCI-Express) (5th gen) (rev 02)

Specs:
Server 2 (Mysql)
ViciBox.i686-4.0.1
IBM-X3100-m4
NTEL XEON QUAD CORE PROCESSOR 2.4 GHZ OR 3 GHZ
HDD 1 TB
RAM 8 GB

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2514 root 20 0 3908 1352 1040 R 49 0.0 145:08.94 asterisk
2047 root 20 0 111m 30m 6984 S 18 0.4 21:06.66 asterisk
2135 root 20 0 22720 7464 2932 S 6 0.1 7:11.51 AST_update.pl
32151 wwwrun 20 0 58800 7576 3508 S 2 0.1 0:00.18 httpd2-prefork
29474 wwwrun 20 0 59428 9304 4712 S 1 0.1 0:00.74 httpd2-prefork
29615 wwwrun 20 0 59368 8300 3872 S 1 0.1 0:00.67 httpd2-prefork
32709 root 20 0 5576 3344 1708 R 1 0.0 0:00.04 agi-VDAD_ALL_ou
16737 wwwrun 20 0 64128 26m 17m S 1 0.3 0:02.76 httpd2-prefork
2138 root 20 0 21056 5764 2848 S 1 0.1 0:46.26 AST_manager_sen
2144 root 20 0 22684 7452 2844 S 1 0.1 1:25.31 AST_VDauto_dial
4236 wwwrun 20 0 62400 24m 16m S 1 0.3 0:03.70 httpd2-prefork
19570 wwwrun 20 0 63200 24m 15m S 1 0.3 0:02.10 httpd2-prefork
22401 wwwrun 20 0 62348 23m 15m S 1 0.3 0:01.53 httpd2-prefork
24809 wwwrun 20 0 59428 8832 4288 S 1 0.1 0:01.14 httpd2-prefork
27211 wwwrun 20 0 59420 9136 4580 S 1 0.1 0:01.00 httpd2-prefork
27314 wwwrun 20 0 58932 8464 4276 S 1 0.1 0:00.63 httpd2-prefork
27318 wwwrun 20 0 58800 8608 4328 S 1 0.1 0:01.02 httpd2-prefork
28823 wwwrun 20 0 59404 8284 3928 S 1 0.1 0:00.62 httpd2-prefork
29231 wwwrun 20 0 58904 8280 3956 S 1 0.1 0:00.41 httpd2-prefork
30218 wwwrun 20 0 58872 8148 3868 S 1 0.1 0:00.26 httpd2-prefork
30959 wwwrun 20 0 58872 8188 3896 S 1 0.1 0:00.34 httpd2-prefork
31289 wwwrun 20 0 58800 7400 3336 S 1 0.1 0:00.28 httpd2-prefork
32575 wwwrun 20 0 58800 7392 3332 S 1 0.1 0:00.03 httpd2-prefork
1886 mysql 20 0 952m 119m 5188 S 0 1.5 0:01.17 mysqld
8595 wwwrun 20 0 58932 8880 4564 S 0 0.1 0:02.63 httpd2-prefork
9884 root 20 0 23700 7168 1748 S 0 0.1 0:01.25 FastAGI_log.pl
11938 wwwrun 20 0 59548 9616 4968 S 0 0.1 0:01.88 httpd2-prefork
13399 wwwrun 20 0 59500 9744 5108 S 0 0.1 0:01.65 httpd2-prefork
14472 wwwrun 20 0 62136 22m 14m S 0 0.3 0:01.83 httpd2-prefork
16738 wwwrun 20 0 59768 20m 15m S 0 0.3 0:02.14 httpd2-prefork
17424 wwwrun 20 0 59780 21m 16m S 0 0.3 0:02.05 httpd2-prefork
17567 wwwrun 20 0 59664 9792 4820 S 0 0.1 0:01.83 httpd2-prefork
19374 wwwrun 20 0 61608 21m 13m S 0 0.3 0:02.31 httpd2-prefork
19389 wwwrun 20 0 59528 9.9m 5292 S 0 0.1 0:01.39 httpd2-prefork
19521 wwwrun 20 0 61616 24m 16m S 0 0.3 0:01.84 httpd2-prefork
20094 root 20 0 23728 7164 1748 S 0 0.1 0:00.77 FastAGI_log.pl
20266 wwwrun 20 0 58936 8664 4456 S 0 0.1 0:01.92 httpd2-prefork

[mav2287]

Have you looked at your apache logs to see if it is actually a web server issue?

[heartzzzzz]

It was a apache configuration problem, tweaked the prefork file. Issue is solved