This is a quick link to my standard troubleshooting list; the first tip I would recommend trying is running FxSound as Administrator.
Here’s another tip you could try.
The first thing you’ll need to do in order to be able to perform it, is click on to Tools > Folder Options > View in the menu bar on top, and enable “Show hidden files, folders, and drives.”
Either way, if it doesn’t work, you can simply change the folder name back to the previous one.
However, please note that this will probably erase all your custom-made presets, as well as all the bonus presets you’ve loaded in.