'cucle' button causing glitches

Something I had not noticed on previous versions of Cubase that is happening now.
When I hit the ‘cycle’ button, either using the on screen button or via the Mackie Control surface, the Disk bar in the Asio performance meter peaks and causes a glitch in the audio playback. This is happening with a project that simply has a single NI Battery 3 drum loop, no audio clips and nothing in the pool. It also happens on more complex projects. I am using Cubase 6.0.5 64 bit on 64 bit Win7, Motu 896HD firewire interfaces and a Mackie control universal surface. MPU is Intel quad core Q9400 2.66GHz, 8GB RAM and several 500GB WD Caviar Black HDD’s. It seems odd that the cycle button would require significant disk access.