Signing a windows screen saver file (.scr) results in a corrupt file

[nk111]

When I try to sign a windows screen saver .scr file the signing completes without errors. The file is properly signed and can see signature information in the file properties.

But when I try to run the signed screen saver I get an error message like this:

telling me it can't be run because it might be corrupted.

Any ideas?