I already told you that iOS 4.0.1 could be released by Apple today to solve the problems with the signal, so I warn you to be careful not to give an iTunes update to your phone, because you might wake up with it blocked for a long period of time. Apple attributed the signal problems to a bad baseband calibration, but it will certainly take the opportunity to block the exploits used to jailbreak/decode, and I for one doubt that the Dev Team will be in a hurry to release others too soon.
In conclusion, be very careful with iTunes today and all week because iOS 4.0.1 could appear at any time and an update has a good chance of leaving you without the possibility of using the telephone function of your iPhone.
