Insufficient Memory message In NT4

I am running an NT 4 Server with Citrix Metaframe on it and have only 4 clients connecting to it. Up until recently and there have been no changes, all has been well, but now none of my users can open MS Word97 as it displays that there is insufficient memory when there can be no other applications running. The machine has 128mb RAM and the paging file size is at the maximum.
thanks in advance