Recently Musician's Friend had the Mackie CRX-2 powered speakers on sale for $50 (reg. $179) a pair. I bought two pairs to experiment with for audio installations. They seem decent enough for their size and price but both are exhibiting a very inconvenient flaw. When playing music through them from my MacBook Air, even a moderate volume pop ballad, the sound completely cuts out when I try to get any decent volume level from them. It's like an overload protection kicking in way too early. Lights are still on, but no sound. Anyone else have these and seeing a similar problem, and maybe have a work-around? There's a firmware update available on the Mackie site but it can only be run from a PC, (I'm currently all Mac) and there is no indication what if any issues it addresses. Anyone know?