I would open activity monitor and while you use your Mac look at the number of pageouts in the system memory tab. Although 4gb may seem like alot you may be running low on ram while running all of those memory hungry applications at once. I've never seen that particular message but I have 12gb of ram and very few pageouts regardless of what I'm doing.
Here's a link about activity monitor
Thanks so much for the help. I opened the Activity Monitor window and here's what I found:
VM size: 171.82 GB
Page ins: 26.84 GB
Page outs: 6.52 GB
Swap used: 59.00 GB
Free: 31.7 MB
Wired: 838.9 MB
Active: 2.10 GB
Inactive: 1.05 GB
Used: 3.97 GB
I would send a screen shot of the window, but don't think I can do that here. Any solutions?
Don't know exactly which iMac you have but I would suggest adding at least 4gb more ram (two more 2gb sticks). If the $$ are available I'd go with 8gb more (two sticks of 4gb) It's easily done and can be had from a reliable source here
4gb for about $30 - 8gb for about $50
I have 12 gb and here's a look at my Activity monitor, notice a difference?