That's infuriating.
The file is fine, the digital signature is fine, it's just internet explorer being stupid (probably what it's unhappy about is the use of sha1 in the digital signing key, which is being gradually phased out by browsers; they are supposed to report something like "the signature is valid but should be updated soon").
Just choose to keep the file when IE asks you, or use a different browser.
Hopefully they will fix this, until then just ignore it.
In the future I will have to experiment with changing the digital signature algorithm to see if there is something that can be fixed to appease the monsters.