Why can't my card reader read PQI cards?

Bit of an odd one.

Ever since doing the firmware/hack upgrade on the CF cards for my 400D I've had to use the card reader (connection/hang up probs). Not an issue on my two 'hacked' Sandisk 4GB CF cards, on insertion they work perfectly. Using the PQI card (same hack applied in exactly the same way), no automatic recognition of it being in there and it says 'insert disk'.

I initially used a USB connected card reader to apply the hacks and it worked fine on all three cards however I don't have this to hand at the mo. As such have to use the inbuilt card reader in the Dell which is struggling with the above problem.

Tried upgrading the firmware (of the card reader) but to no avail.

All photos perfectly viewable on the camera itself.

Any ideas? TIA

Are all three cards formatted using the same file system? Partitioned the same? Just a thought.

To my knowledge, all identical. The difficulty of course is in access - can't do it via the camera. Can't do it via the inbuilt card reader. May need to wait until I can get to my USB card reader (at least another week or two).

The worry is that it is full of snaps from my latest holiday in Morocco. Very fearful I will not be able to retrieve them.

You hacked the firmware of Sandisk cards. That does not mean that the same firmware update was necessarily compatible with your PQI cards, which it sounds as if you did this!

Any cunning plans in that case?