I know this is an older post, but I figured I'd post the solution that worked for my 16gb PNY drive. This solution comes as a sort of 'reset' tool directly from PNY..

I was having a similar issue with my 16gb PNY Attache USB 2.0 drive where I could see it in Disk Management, but it showed up as 0mb size, and when I tried to open it, but I'd get a message saying there was no media inserted. After ~3 days (an eternity in my book) of constant troubleshooting, recovery tools, testing (all this even on a Mac), etc. I FINALLY found a solution.

Before I give you the link I'll warn you (and anyone else who might use it) that the tools on this page will erase your drive. I think in the OP's case that's OK, but I wanted to give that little disclaimer just in case.

Without further ado, here is the page of tools directly from PNY that will help you basically reset your flash drive back to factory settings/configuration! Once you're on this page, click the downloads tab and download the appropriate tool. In my case, I tried the first one (Ufix I) which didn't work, so I used the second one in the list (Ufix II) which beautifully restored my flash drive to it's original working form.

Good luck,

Jake