Iphone 3g 16gb
Right baseband...
Right Version (2.2)...
Jailbreaked ok
Installed Sbssetings and Mobile terminal...
Installed yellowsn0w 0.96...

Every single method posted tested.

Everytime the same result: No SIM

One of the times i've made the unblock methods i had service but it failed 3 to 4 times a day, but 48 hours after... No SIM

I've lost count of the reboots, the -c -r and -q in mobileterminal, the airplane on and off, just about everything

I'm getting sure that I have a Ibrick!!

Does anyone have a small idea that can help me?

Thanks!

Dfu restore to 2.2. And try with supported sim. If it works try to unlock again

Have you ever used a TurboSim or something similar?

In fact, a restore should clean everything and get everything working again.
If it is still with No Sim message, your iPhone got a hardware issue.