I'd still sort of guess driver or BIOS issues, even if across the board on brands - anytime they release a new chipset, it seems like like everyone (the mobo makers) rushes to get all their mobos out (and often with little regard to whether everything really works correctly or not, so individual manufactures at times even overlook problems, in order to be on the market from the getgo and not lose any sales. This is one reason I asked about any particular brand.
A little background, hope not to bore you, the manufacturers take the base mobo design and modify, add the changes they want for their line of boards, say X1, X2, X3 etc using that particular ref design for the chipset. While doing so, they may find problems with the chipset (i.e. USB - LAN -video- etc), but they seldom 'share' that info with the other manufacturers and may be slow in sharing with the chipset maker (they think this gives them an advantage if they can 'fix' it i.e. "ours work, yours don't ha-ha'. Next they send the mobos out to other places for them to review , bench and test...normally this is a short period, say two weeks or so, but it gives the reviewers time to test and write their articles so they can all release them on the product release date. Now this is where a lot of problems are identified, and often the chipset maker can issue a fix, which may or may not be implemented before release, if not it's generally available on the mobo makers web sites in the form of Driver or BIOS updates come the release date or soon there after. There are of course exceptions, when the P67/1155 (Sandy Bridge) came out there was a problem in the chipset concerning SATA, and for a short period they basically had to recall the mobos and pull them off the shelf's till the chips were changed. This is one of the big reasons I don't buy for my own personal/business use until a month or two after the release. This also gives them time to get the BIOSs up to speed somewhat especially with DRAM and XMP, which is usually a long ongoing process