Plug it into a PC if you can, and check what filesystem its formatted as. Then try reformat it to fat32.
And just to clarify, the "HC" part in SDHC simply stands for "High Capacity", which generally means SD cards larger than 2GB.
Some devices can have issues with certain SDHC cards (like my Wii and my N7B), but to my knowledge TF101 is not one of those devices.
Of course, that said, that doesnt mean some weird china-knockoff brand will work, but Lexar isnt that bad and shouldnt pose any issues imo.
So uh, yea, try reformatting it to fat32.