Theres a couple of things you can do to fix that issue:
Because of the slow processor in the ally you have to minimize anything running in the background(live wallpaper, mms apps, google voice, etc) press the menu key and goto settings, applications, running applications, and close unwanted apps(be carefull some google and other apps need to run in order for them to work properly, if you screw something up closing an app just restart and it will reload them). Another thing you can try is increase the idle speed of the processor, which is like 245mhz. Change it to the next step up which is 320mhz. It doesnt affect the battery much, but it does make a difference in pandora if the screen goes off and it goes into sleep mode. To do that in velocity 1.2, you have to access it via the menu key, choose settings, velocity settings, cpu settings, and change the 245 to 320. Dont try and overclock the max as it just causes the OS to crash and restart more often. Also if you do experiment with trying to make the phone faster dont apply on boot either in case it doesnt take the clock and reboot setting again after you reboot.
I also had an issue with pandora stopping at around last verse to the end of the song and gets stuck on buffering. I have to change radio stations and skip songs and every song does it around a certain time or so just freezes. Theres a lot of crap with this phone and velocity makes it bearable and actually usable, its still a low end crap phone that doesnt last very long battery wise(replacement usually in a year or so) just tough it out until something better comes up for an upgrade.