I changed the folder locations in my preferences, and then SLP 4 would no longer work. I get "Device Error #1" Open Error: no samplerate or channels available (48000,0,0). When I try to play audio, I get "Device Error #2" "API not initialized".
Problem seems to be related to my WASAPI device. It is selected, and the correct output device is selected (analog), but there are no channel mappings available for it. (tried the digital outputs too - no channel mappings available).
Tried SLP 3, and no problem at all. Changed device from WASAPI to ASIO and then back to WASAPI and the channel number mappings are fine.
Of course there is no way to file a technical support request against SLP 4, even if it weren't the trial version. (they apparently don't think SLP is their product on the support page).
Don't think I'll upgrade to SLP 4. Not ready for primetime yet.