Windows 2003 R2 Extrange Pages/s up to the roof

Hi

Have been a couple of times this week my DC/Exchange Server has gone mad and
forced me to reestart it.

It appears to be executing something that consumes all memory and force it
to use the virtual memory. The perfomance monitor shows the pages/s
indicator up to the roof of the chart.

The task manager instead doesn't show anythyng weird.

I pass Malicious Software Removal Tool to check if there is any virus and it
appears to be not the case.

Just copy the Systernal's Process Monitor to this server so, if it happend
again i can see in more detail what is happening.

My question is, any body have an idea that could help me to narrow the
problem?

thanks in advance