Here's how to get your self out of a pickle saving over a an FXB file with another FXB.
Open your vst host that has the same midi file preset & re-save this as the FXB file you accedentally saved over.
As I am so kind I have also put the fxb on my site for a free download as it took me so long to get no where fast finding it out there on the web.
- doesnt seam to exist.
http://www.serious-design.net/TEMP/fxb
username: user
password: Pass
This FXB file is to the Refx Vanguard