High Apache load jump for no apparent reason

[crkgb]

[EDIT] Problem solved, see the next post.

Hi I am working on setting up my vBulletin test site for public release tomorrow. At the moment there are no active users on my website, just two admins working. I encountered a strange problem yesterday - every page on website got much slower than before, Apache load to process every page increased significantly. Trying to pinpoint the issue, I looked at Debugging Info table. There is a big gap in time spent between two requests:

Datastore Setup:
Time Before: 0.00348 seconds
Time After: 0.03787 seconds
Time Taken: 0.03439 seconds
Memory Before: 233.430 KB
Memory After: 2,178.645 KB
Memory Used: 1,945.215 KB

Notice the huge jump in memory consumption. And then the very next request:

Session Handling:
Time Before: 4.82031 seconds
Time After: 4.82092 seconds
Time Taken: 0.00061 seconds
Memory Before: 2,420.191 KB
Memory After: 2,420.102 KB
Memory Used: -0.090 KB

Where did my 4.8 seconds go?
Just a couple of days ago the whole page was processed in under 2 seconds.

Some site information:
vBulletin® 3.8.0 Beta 2
Lots of mods are installed, but no new mods added recently. One custom built component was slightly modified yesterday - may be just a coincidence.
Webserver: Apache 2.2.8
PHP (Apache module): PHP 5.2.4
eaccelerator-0.9.5.3
Memory:

cat /proc/meminfo
MemTotal:      2074584 kB
MemFree:         78552 kB
Buffers:         77536 kB
Cached:        1731528 kB
SwapCached:         52 kB
Active:        1103964 kB
Inactive:       830804 kB
HighTotal:     1178560 kB
HighFree:        17116 kB
LowTotal:       896024 kB
LowFree:         61436 kB
SwapTotal:     1951888 kB
SwapFree:      1951772 kB
Dirty:              64 kB
Writeback:           0 kB
AnonPages:      125648 kB
Mapped:          40388 kB
Slab:            50248 kB
SReclaimable:    38052 kB
SUnreclaim:      12196 kB
PageTables:       2552 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   2989180 kB
Committed_AS:   393956 kB
VmallocTotal:   118776 kB
VmallocUsed:      4584 kB
VmallocChunk:   113992 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
HugePages_Surp:      0
Hugepagesize:     2048 kB

CPU:

admin@www1:~$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping        : 9
cpu MHz         : 2411.643
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up pebs bts cid xtpr
bogomips        : 4826.65
clflush size    : 64

The attached screenshot shows what happens to the system when a vBulletin page is requested.

Does anyone have an idea what could be the reason?

[crkgb]

Problem found. By turning on and off different mods we singled out the guilty party - the front page slideshow. It was putting acceptable load on server in test mode when there were just 3 news to display, but it went totally out of hand after we added content and it was rotating 10 news articles. So the bad deal is that we lost a good looking part of our main page. The good deal is that now our pages get processed really fast - from 0.4 to 0.8 seconds