I get this error too. I tried chdman.exe -verify on the file and it says:

Input file: gtrfrk2m\929jbb02.chd
Error opening CHD file: invalid file

So either the file is not a valid CHD file (I am not familiar with the format but maybe an invalid header?) or else a bug was introduced into the chd_open routine used by MAME which causes it to think this file is an invalid CHD file. Obviously the MAME team would have to look at this to figure it out.

> Hi Roman,
>
> Remember me? Guess not, it's been a while;-) We talked about clrmame in the very
> beginning... and never ever dared to dream that it would come as far as it is
> now;-)
>
> I discovered this thread hunting for a solution for the VERY SAME problem! Ik
> have the file 929jbb02.chd, I can access it, move it, copy it, delete it,
> whatever.... But clrmame 3.101a together with MAME32 1.16 reports:
>
> Guitar Freaks 2nd Mix Ver 1.01 (GQ883 VER. JAD) [system: System 573 BIOS -
> folder: gtrfrk2m - size: 512kb]
> integrity check failed: 929jbb02.chd [reason: can't access file]
>
>
> I have disabled the only virus scanner on my system before scanning. I'm not
> behind a software firewall a spyware blocker.
>
> However!
> Also the GUI of MAME 32 1.16 reports the file missing. So maybe it's a problem
> in MAME 32?
>
> ps: I've tried to download another version of the CHD which gave the same
> result.
>
> I checked some more with Mame 1.16 guitar freaks games:
> Although clrmame, after "deep scan", reports a perfect set (besides the issue
> mentioned above), MAME32-116 reports problems with guitar freaks 3, 4 and 5.
> Despite the fact that MAME reports gfreaks missing (black square) these games do
> launch, reporting that "one or more roms/chd's are incorrect".
>
> I think there's a problem between MAME and CLRMame?
>
> Hope to hear from you, and please let me know if I need to test some more,
>
> Greetz,
>
> |\/|arc
>
> > Looks like a different task (virusscanner etc) is accessing the file while
> cmpro
> > wants to access it. I will have a look at it later at home but in the meantime
> > you can try to disable your virusscanner while scanning, turn off other
> programs
> > which may access the file and so on.
> >
> > *edit* ok, I've looked at the source code and that error appears when a
> chd_open
> > fails, i.e. assuming the file exists, some other task blocks the access.
> >
> >
> > Roman Scherzer
> >
>