I am Not running the Valhalla cab & my GPS works fine. However my phone is unlocked with 2.31 & running NFSFAN's 1.15 ROM.
Try this thread but it will void your warranty if aplicable.
http://wiki.ppchaven.com/index.php?t...IX_VERIZON_GPS
You can probably skip the last step in the process. Since you probably let the customizations run you'll have to go back to a pre-GPS radio to get the GPS working.