We had similar issue with Transcend IDE flash drive (4G).  Our solution was to give up on this brand all together.  Not 
that there bad but Transcend and QNX don't seem to be compatible for some reason. 

At the time I didn't feel like paying big money to have this issue fix (custom engineering).  Plus from experience, 
through foundry, the feedback from QNX is on the low side.

> We're using a Transcend Compact Flash, model TS2GCF266, which is 2G, 266X SLC.
>   The device does support the FLUSH CACHE command, and it works fine with sync
> =mandatory.
> 
> However, if I create a qnx6 fs on the device and then write several megabytes 
> worth of files, it gets a low-level error and the device seems to go into some
>  sort of write-protect mode where we have to cycle the power to clear it.
> 
> What's odd is that we can do the exact same thing with qnx4 fs, and we can 
> write every sector on the device with dd.  In fact, I created a qnx6fs on 
> another similar CF, and dd'ed the entire image to the "bad" flash without any 
> problem.  The resulting CF boots up just fine, but any attempt to write a 
> large file to it produces errors in the slog and the device stops allowing 
> writes.
> 
> I've tried everything I can think of, including sync=none, turning off DMA, 
> etc., and it makes no difference.  "Something" that qnx6 fs is doing is 
> causing this flash device to give an error.
> 
> I've reproduced in in various different machines, with two different CF 
> modules, HOWEVER, it doesn't happen with every module.  I have a third CF of 
> the exact same make & model, and it does not exhibit the problem.
> 
> I loaded "devb-eide eide verbose=5,master=verbose=5 cam verbose=5" and have 
> the slog output of the resulting error, if anyone wants to look at it.  It 
> doesn't seem to have a lot of info, other than that it was doing a write of 
> 64K bytes and then the next thing is a "reset completed after ~300ms".
> 
> If it was just a single device, I would dismiss it as bad, but two different 
> ones?
> 
> Thanks,
> lew

Update..... we took the slog info showing all of the commands that were issued to the drive and wrote a little program 
to reply them, and it reproduces the problem, completely independent from the qnx6 fs.  So it has nothing to do with the
 filesystem, but simple the pattern of writes that was done to the flash.

We then ported the test program to Linux and the problem occurs equally well.

So bottom line, QNX is not at fault and we will pursue this with Transcend.

Thank,

lew