After a cold boot, I'm able to copy gigabytes of files from a 16GB SD card in the internal card reader, even with many other programs running. But when I put the computer to sleep mode and then wake it up, I'm only able to copy a file or two at a time before I get a "There is not enough memory to complete this operation" error, followed by an automatic dismount and remount of the SD card. The only way to get it working again is a restart. The SD card works fine, as I don't have this issue when using an external SD card reader. There is plenty of memory free (6GB of 16GB). I've reinstalled the card reader driver from Dell.
Any ideas on what to try? Seems like a BIOS or driver issue to me.