MAMEWorld Forums - EmuChat - Now, this one has me stumped.

Hello all... new to the forum, but not to MAME. My first cabinet (that I built for my co-workers), has a full MAME set, runs Hyperspin as the FE (with all videos and themes), has a built-in audio amplifier and dual, powered subwoofers in the base. It looks like this:

Now that you know I'm not a complete noob (wink), I wanted to ask for some help with something that has stumped me recently. I've installed MAME version 146 on four computers now, but on the last one (a small, low-power nettop), I'm getting a "DIFF CHD ERROR: File Not Found" code on ONLY my games that require CHD files (all other games play fine):

Followed by "ERROR: Required files are missing, the game cannot be run." message:

Now, here's the thing. I've tried everything I could find online (yes, Google is my friend), as well as several other tricks, and nothing has allowed CHD games to play. Here's what I've tried:

I have re-installed MAME.
I have copied MAME over from another computer that runs these games perfectly.
I have copied the CHD and zip files of these games from another computer that runs these games perfectly.
I've removed the contents of the DIFF folder (though on my most recent re-install of MAME from the MAME downloads site, I don't have a DIFF folder).
I have used both ROM and CHD files that are compatible with build 146, as evidenced by the fact that I have three other machines using these exact same files just fine (and they also come from a reputable source who updates files regularly and has never given me a bad dump).
My computer is a brand-new build, with nothing but Win7 64-bit installed (no other apps except what came with the machine, Chrome, XPadder, Hyperspin and MAME).
I have no other issues with my PC, Hyperspin or MAME. All other games run fine.

I tried searching these forums for answers, but it seems like I must be missing something simple. Any help at all would be appreciated.