Gal Civ2 Squeak sound glitch on new planet event

I've recently come back to this classic game and have patched to the latest version.

However, when I colonise a planet and before I chose my ethical alignment there is an issue.

An event pops up asking me if I would like to choose the good, neutral or evil option.

The evil option is usually a bonus such as research bonus 33%, etc. 

If I select this, when I click the Turn button or planet selection buttons, the normal sound now sounds like a squeak. 

I reload prior to my colonisation and try to recolonise again and I choose the evil option with what ever new bonus the planet provides and the same squeak sound glitch occurs.

This does NOT happen if I select the Neutral or Good option (which have minimal or no bonus respectively).

Can anyone help ?