Hello:
I saw your post and had a possible solution, so I registered, and here it is.
When on Windows 8.1 I was transferring a-lot of files off my UPnPLAY (Iomega) drive I noticed my laptop hard drive getting warm. It was transferring form the UPnPLAY drive to a 2TB portable USB 3.0 drive. So I checked the internal drive space & noticed it had gone down.
I got a program called "WizTree" to view what was using all the drive space (I was down to 6GB out of 750GB on the internal drive). If you use the program just view the top 1000 files (tab at the top), you'll see the hidden inetcache directory has all the files. You can delete them from this program (it is free, but like I am doing, just give them an optional donation if you can - support programmers). I sorted by file size, then select the first, shift and select the last, then right click and select delete.
I'm installing some new Seagate Windows 8 software for my GoFlex drives, the iOmega I'll work around or do it from Android. In my case, perhaps yours too, it seems to be a bug whereby it uses that directory as an intermediate stage. The files listed by WizTree were the same files I had been moving so I was sure it was NOT malware but simply that the cache had not been flushed afterwards. I did run Microsoft Safety Scanner - it was clean.
I'll see if the software install clears it up - I have not fully installed them yet so it's very likely this is the cause.
Hope that helps...
EricW