Could be a worn or loose drive belt. Un-plug the machine and remove the lid and the back access panel. Check the belt for fraying and/or wear. If okay, pull the belt to see it's tension. It should be taught, if it's not, go to the motor at the bottom of the machine. loosen two of the motors retaining bolts, push the motor down gently, which will tighten the tension of the belt, and whilst holding in position, tighten the retaining bolts.
Re-fit the lid and back access panel and try the machine in the setting where it made the noise. Hopefully this will correct the squealing....Good luck.
Davy Mac, June 2009