said by HIPAR:
There's no GPS compatibility problem with the satellite to earth signals but the uplink from ground terminals might still be a problem for nearby GPS receivers.
No, LightSquared's satellite is licensed for uplink in the 1626.5-1645.5 MHz and 1646.5-1660.5 MHz bands. GPS downlink frequencies are 1575.42 MHz (L1) and 1227.60 MHz (L2).
LightSquared is licensed for 1525-1544 MHz and 1545-1559 MHz for their _downlink_, but at that power level, it won't interfere with GPS.