Unity Started Freezing Periodically

Hi all,

Have had Unity version 4.3 on 25 school computers since the start of February. Has been working without issue so far.
However they recently had updates done to them (Microsoft Updates) which seem to have slowed them right down, causing them to freeze up for about 2 minutes at a time.. (i.e. Unable to select anything in the Unity Application, freely able to use other computer resources)

Just wondering if anybody has any ideas as to what could be causing this issue.
(These machines are brand new this year)

Cheers in advance