Oh for the love of...
Good news is you fixed the problem relating to using dual-core CPU (though it seems a problem with HTT itself; still working fine on my quad). This new problem may well be heat related; console ports tend to overheat the memory before the core heats up (ie cooling doesn't spin up).
Could try lowering graphics and/or setting the cooling higher manually with something like Rivatuner.
On HTT: there's no such thing as a Pentium 4 dual-core. It's actually a single-core CPU with HTT. HTT creates a second
virtual core. Though turning it off might fix some compatibility issues, it (your PC) is probably faster in day-to-day use with it enabled.