Digital Home Thoughts: Strange SDHC File Deleting Issues: Has Anyone Else Had This Problem?

A couple of months ago, I picked up a 16 GB Patroit SDHC card from Dell - they had them on sale and I think I paid a bit under $80 with tax and free shipping. It's a Class 6 card, meaning it's fast enough to be used in an HD camera recording 1080p video. The only thing about SDHC cards that makes me grumpy is the fact that my Dell 24" monitors have built-in memory card readers, but they're not compatible with SDHC cards. To solve this problem I purchased a couple SanDisk MicroMate readers - they plug into the USB port on the side of the monitor, and give me the ability to read and write to SDHC cards without hassle...until I tried with the Patriot 16 GB SDHC card. For some inexplicable reason, I can't delete files off the card when it's connected to the SanDisk reader. I can write files, but not remove them. I thought at first the SDHC card was in locked mode, but it's not. I can delete files off the SDHC card when it's in the SD card slot on my XPS M1330 laptop, but when the SDHC card is in the SanDisk reader, I can't delete the files - and I've tried in multiple PCs, and multiple USB ports (both monitor and tower ports). I'm baffled and can only theorize that there's something that's slightly incompatible between the Patriot SDHC card and the SanDisk MicroMate reader.