I have the same problem with my S2 LTE (stock, ICS, with maybe a dozen non-factory apps. About 10 months old now). Periodically, I'll get the same message. I would try reformatting through the phone, but it wouldn't reformat. I tried my PC and it would tell me the card needed to be reformatted, and I would reformat using it (Windows 7, whatever its default formatting setting is). Than I heard that there may be an issue with using the PIN screen lockout security feature that messes up the in-phone formatting tool. I switched to the Pattern unlock mode, and then next time I had a blank sd card message, I was able to reformat through the phone. Weird, but I can now reformat with my phone.
My biggest gripe is that I have to reformat so often. I went about 6 months problem free. Now, I get the blank card message almost everytime I try to connect to my PC (via USB and Kies; I haven't tried transferring files via wifi yet). Once or twice, its happened right after power up. I use a Lexar Pro 32gb card, but never get more than a few gb onto it before the problem hits.
I can reformat and use the card again afterwards, so I don't think my card is the issue (or is it??). I'm guessing something (software, app, one of my files, the phone itself) is messing up the filesystem, as opposed to any physical issue with the card. But its virtually impossible to pinpoint for someone with limited knowledge and tech skills like me
Everything works fine for awhile and then blam.
Any suggestions anyone? I hate having to jump through hoops everytime.