iPhone OS 3.1.3 includes the following fixes and improvements:
iPhone OS 3.1.3 is available for all iPhone and iPod Touch models.
or Geohot to provide an update on how the latest iPhone OS impacts a jailbroken/unlocked iPhone as you could end up bricking your iPhone .
then download and install iPhone OS 3.1.3 via iTunes and please let us know how it goes and if it fixes the issues mentioned above if you were facing them.
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iPhone OS 3.1.3 (7E18) also updates the baseband firmware, so if users who have software unlocked your iPhone should avoid it.