Windows 7 fonts installed but missing and not viewable in fonts folder

Hi everyone...(sorry not sure if this is the right forum to post this).

I have specific fonts downloaded from fonts.com in the last 1 year that have given me trouble - including Din and Biome (and I think a couple of others). These are Open Type fonts. I also have other open type fonts that work fine.

The fonts install and work fine until I restart the computer. They then show as missing in any application even though none have been uninstalled, they also don't appear in the fonts folder. If I install them back into the fonts folder a pop up says "this font is already installed, do you want to overight" (or something similar). As a temporary fix I say "ok" it reinstalls the fonts and then they work fine.

Any thoughts? Very frustrating having the fonts disappear on every restart.