I'd start loading that gun.... you might need it....
I'd also check NA and HDD in another PS2.... then it boils down to a problem with your PS2....
1. clean the slot and plug of the NA and PS2 with a toothbrush (preferrably new one)
2. check all the fuses that are associated with the power and use of the NA
by this point it could be any chip on the board... and unless you have weeks of nothing to do... it might be advised to get a new PS2....
PS3 Slim 320GB
PS2 v11 exploit w/300GB Maxtor
PS2 v10 exploit w/80GB Samsung - Network Games
PS2 v10 exploit w/60GB Samsung - Network Games
PSP 1001 3.52M33 w/10GB total storage
NDS DSReal 4GB