The EU version of the dongle supports two frequency bands: 433.420 or 433.920MHz and 868.350 or 868.950MHz.
The 868Mhz band isn't allowed in the US, so that version does 433.420 or 433.920MHz and 310 or 315MHz. The 310/315MHz band is referred to as the "High Band" in the RFPlayer documentation, even though it isn't.
My Oregon Scientific devices use 433.920MHz. My Visonic device uses 315MHz. Unfortunately, X10 RF uses 310MHz. So you can't listen for X10 transmissions (like from a PalmPad) if you use Visonic. Or vice versa.
There are probably other conflicts that I haven't run into. If you have, please post them here so others are warned.