GSM-No Service-What problem iphone 3G

Hello,I have a problem with my iphone 3G: if i turn on 3G i have full signal but when 3G is turned off my phone goes in Searching... mode and after that i receive No Service. I looked into the log files in /var/logs/CrashReporter/Baseband and ive found something interesting:STATE DUMPReason: modem reset: AT response timeoutHow can i solve this issue? Is there a way to reflash the Baseband during iTunes Recovery?This is a major problem because when Im out of a 3G cell i get No Service and i have to check my phone to restore my network.Firmware: 3.0Baseband: 04.26.08Bootloader: 5.9 iphone OS 3.0