Many ppl have this issue if thier ring tones are stored on the card. Are yours?
Also see the reg edit below and more tweaks can be located
here.
Force EV-DO/1X, quicker ring response
To do this, you will need your MSL, which only Sprint (or your provider) can provide you. Verizons cods is 000000 Open up the phone app and dial ##778 (PST). You will be asked to enter your MSL. Enter it, and you will be brought into the provisioning of your phone. From the top left, select Modem Settings. On this page, your Slot Cycle Index (SCI) is how often your phone polls the tower for incoming calls, etc. This value is 1.28 seconds multiplied by 2^value (i.e 0=1.28 secs, 1=2.56secs) with 0 fastest, 7 slowest. The default is 2, but lowering it to 1 hasn't noticeably affected my battery life, and roughly 2.5 second (SCI 1) response time is far more reasonable than roughly 5 seconds (SCI 2).