debian lenny 64bit,
Xeon 2.3Ghz , 4GB Ram

please, provide more information than just one screenshot. as a starter, new values per second, load on the db server, item details, zabbix item and trend cache usage data.

Zabbix server is running Yes -
Number of hosts (monitored/not monitored/templates) 1337 1286 / 1 / 50
Number of items (monitored/disabled/not supported) 4238 3848 / 214 / 176
Number of triggers (enabled/disabled)[problem/unknown/ok] 2655 2652 / 3 [120 / 6 / 2526]
Number of users (online) 4 1
Required server performance, new values per second 77.14 -

/etc/init.d/mysql status
/usr/bin/mysqladmin Ver 8.42 Distrib 5.1.44, for debian-linux-gnu on x86_64
Copyright 2000-2008 MySQL AB, 2008 Sun Microsystems, Inc.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Server version 5.1.44-3~bpo50+1
Protocol version 10
Connection Localhost via UNIX socket
UNIX socket /var/run/mysqld/mysqld.sock
Uptime: 3 hours 31 min 30 sec

Threads: 145 Questions: 4364089 Slow queries: 133 Opens: 560 Flush tables: 1 Open tables: 220 Queries per second avg: 343.899.

top

top - 17:44:07 up 3:39, 2 users, load average: 0.98, 1.72, 2.25
Tasks: 302 total, 1 running, 300 sleeping, 1 stopped, 0 zombie
Cpu(s): 28.3%us, 4.1%sy, 0.9%ni, 53.9%id, 12.5%wa, 0.0%hi, 0.4%si, 0.0%st
Mem: 3931288k total, 3414940k used, 516348k free, 223320k buffers
Swap: 4883720k total, 8248k used, 4875472k free, 1364120k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
27473 zabbix 25 5 17968 852 644 S 4 0.0 0:07.31 zabbix_agentd
4 root 20 0 0 0 0 S 2 0.0 0:00.28 ksoftirqd/0
1811 root 20 0 0 0 0 D 2 0.0 1:48.00 flush-8:16
1879 zabbix 25 5 120m 12m 10m S 2 0.3 0:04.56 zabbix_server
6517 zabbix 25 5 5896 648 544 S 2 0.0 0:00.01 fping
6549 root 18 -2 19088 1336 852 R 2 0.0 0:00.01 top
1 root 20 0 10316 636 584 S 0 0.0 0:00.50 init
2 root 20 0 0 0 0 S 0 0.0 0:00.00 kthreadd
3 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/0
5 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/0
6 root RT 0 0 0 0 S 0 0.0 0:00.05 migration/1
7 root 20 0 0 0 0 S 0 0.0 0:00.24 ksoftirqd/1
8 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/1
9 root 20 0 0 0 0 S 0 0.0 0:00.32 events/0
10 root 20 0 0 0 0 S 0 0.0 0:00.27 events/1
11 root 20 0 0 0 0 S 0 0.0 0:00.00 cpuset
12 root 20 0 0 0 0 S 0 0.0 0:00.00 khelper
13 root 20 0 0 0 0 S 0 0.0 0:00.00 netns
14 root 20 0 0 0 0 S 0 0.0 0:00.00 async/mgr
15 root 20 0 0 0 0 S 0 0.0 0:00.00 pm
16 root 20 0 0 0 0 S 0 0.0 0:00.00 sync_supers
17 root 20 0 0 0 0 S 0 0.0 0:00.01 bdi-default
18 root 20 0 0 0 0 S 0 0.0 0:00.00 kintegrityd/0
19 root 20 0 0 0 0 S 0 0.0 0:00.00 kintegrityd/1
20 root 20 0 0 0 0 S 0 0.0 0:00.11 kblockd/0
21 root 20 0 0 0 0 S 0 0.0 0:00.10 kblockd/1
22 root 20 0 0 0 0 S 0 0.0 0:00.00 kacpid
23 root 20 0 0 0 0 S 0 0.0 0:00.00 kacpi_notify
24 root 20 0 0 0 0 S 0 0.0 0:00.00 kacpi_hotplug
25 root 20 0 0 0 0 S 0 0.0 0:00.00 kseriod
28 root 20 0 0 0 0 S 0 0.0 0:00.00 kondemand/0
29 root 20 0 0 0 0 S 0 0.0 0:00.00 kondemand/1
30 root 20 0 0 0 0 S 0 0.0 0:00.01 khungtaskd
31 root 20 0 0 0 0 S 0 0.0 0:01.00 kswapd0
32 root 25 5 0 0 0 S 0 0.0 0:00.00 ksmd

in this exact attachement I'm monitoring gateway on LAN with icmpping, but I have this problem on other hosts too, not only on this one

cat /proc/stat

cpu 762691 24167 114222 1536806 351652 1184 10124 0 0
cpu0 380630 13860 60459 711216 218355 599 5259 0 0
cpu1 382061 10306 53762 825590 133297 585 4864 0 0
intr 17040549 89 5 0 0 1 0 0 0 1 0 0 0 0 0 0 0 2052675 0 145584 0 0 0 0 0 0 0 0 0 6138414 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 54083590
btime 1295010305
processes 72977
procs_running 1
procs_blocked 0
softirq 23007644 0 5638713 2773 6482326 2066410 0 19 2499776 352 6317275

sorry, but this looks like a support issue, not a bugreport.
you mentioned on irc that downgrading to 1.8.3 doesn't change anything, thus this is most likely a performance/configuration issue. note that iowait on the system you posted data for (didn't see what system that exactly is) was 12.5 - fairly high. a longer term data gathering would be suggested, but currently this looks like a performance/support issue to me -> closing