From your story, it indeed seems that your hdd is not reading fast enough. You could try using cIOSX rev21 and install it to IOS249, using IOS58 as base. It is said, that using IOS58 as base is faster, although wen a mod tested it, he reported that he did not notice any difference. It is worth a try though. Other than that, I can only suggest trying another loader, or another HDD.