This is maddening for both of us, I'm sure.  I'm tempted to uninstall everything, start with a clean install of FSX and add nothing but the 757 and see if Traffic X or some other version of FSUIPC or something is causing a conflict.  I suspect, however, that it is my Dell's onboard sound hardware and there's nothing that is going to work.  They're doing something different with the way their sound works than other devs.  I hope they stop :-)

I would think yours more likely to be some weird conflict, though, since I have never heard of anyone else having an unfixable power issue.  At least the sound issues are fairly well documented.