Hi some new experience from me:
As some other people wrote, the problem with network adapter sometimes appears together with other problems, such as with USB ports or with disks in AHCI mode (as in my case). So I performed some experiments:
If I changed "Delay for HDD" to 0 seconds in BIOS, the problems occured almost in each start of the computer. The higher value of "Delay for HDD" I set, the lower is the frequency of occurence of these problems. If I set it to 15 secs (which is max available value), the problems occur only in less than 10% of PC starts (its just a guess). But they still occur sometimes...
So I continued in expermionets:
I changed the SATA2 prots which I use for disk drives. Before this change I used these ports:
SATA2_0 for system SSD (OCZ Agility 2, 60GB)
SATA2_1 for data HDD (Seagate Barracuda, 750GB)
SATA2_2 for SONY Optiarc DVD-RW
I changed it to:
SATA2_0 for SSD
SATA2_2 for HDD
SATA2_4 for DVD-RW
Other ports are blank. Looks like that this change also reduced the occurence of the problems rapidly, even when i set the delay for HDD to 0 seconds.
Later I also disabled everything in BIOS what i am not using right now, such as:
eSATA controller
onboard Firewire
GSATA ports
at least the POST is now much faster
Maybe it helped a little bit too, but the testing takes a lot of time because the problems appear nondeterministically...
Definitely, the problems are caused by faulty detection of the NIC (but it is not very surprising
, because when I disabled the NIC in BIOS
and tested it for few days (with more then 30 starts or restarts of the PC), the problems had never occured.
Now I plan to test it with NIC enabled but the network cable unpluged (also for at least tens of starts).
It would be good if others who have these problems would do same settings and testing as me, to decide if it really helps...