Probable causes:
1- To many applications running at the same time.
2 - To many documents, or to large, open at the same time.
3 - Not enough page space.
Possible solutions:
1 - Close some applications. Check to disable some preloading of some applications.
2 - Look if you can add some more RAM. Try working with less documents at the time.
3 - On a 32 bits system, set the page file so that, when added to your ram, it totals about 4 Gb (4096 Mb)
If you have a 64 bits system, set it to about twice the installed RAM.
Kualinar, March 2010