Nuendo 6.5 - Lag issues

Hi, I’m using Nuendo 6.5 at my place of work on Windows 8.1 and am experiencing lag issues when performing certain commands such as ‘silence’. It appears to take about a second or two for me to be able to then play audio or perform another command. I’ve asked the IT help and they insist that the new PCs we’re using are more than adequate for the demands of Nuendo. Apparently the graphics card has nothing to do with it either.
I’m unfamiliar with the advanced settings, has anybody else experienced this or have a suggestion?
Thank you,