I can't add much more to what's been posted here already.
Reset or clear the CMOS.
You're using DDR2-667 memory? Then, for the E4300, you need to begin by running it at DDR2-400, since you have a processor for an 800 Mhz FSB.
You would then slowly raise the FSB in increments and the DDR speed in the same ratio. Hopefully, you would at least be able to run these modules as DDR2-533, and with luck, you might get them to run as DDR2-667 -- IF -- IF you can safely and stably over-clock the E4300 that far.
Otherwise, you would want to run the memory modules in a ratio to CPU speed other than 1:1. For instance, with CPU-to-RAM ratio of 4:5, you would hope to run the E4300 processor at 9 x 266 or nearly 2.4 Ghz -- a 30% over-clock. You would set the memory to run at their rated, stock speed of 667 (double-data-rate) Mhz. That is, the ratio between 266 and 333.5 is 4:5.
You might be able to slightly over-clock the memory, and you may get away without loosening the latencies. You might even be able to tighten them a tad. That is, you might shoot for 2.55 Ghz CPU-speed, and running the memory at DDR2-700 -- at a ratio of 4:5.
But that all depends on the quality of your memory modules, or how "elastic" they are to running above their spec'd speed.