It’s most probably because you have an other audio device active, other than your regular sound device (like an USB headset, or other external sound card / devices). Or the rate in the driver of your sound card is set too high. StreamWhatYouHear supports up to 48kHz in 16 bits. Try switching to this setting and I’m sure it’ll work. =)
Same problems in W8.1 64 bit. Crashes when SWYH is started up. The problem is not my soundcart which has the right configuration.
When SWYH is started up right and it is not crashed, than SWYH cannot find the audio server/adaptor, and then it crashes after about 1 minute. Although the wireless adaptor is seen in Windows there is no communication.