Macbook limited to amount of memory resources

So this kinda irratates me.

I have the 2.2 blacbook, 4gb ram, 320gb hdd.

Now when I first bought my macbook, I did not use Illustrator or Photoshop CS3 (for both).

Now 1.5 years in, I am using Illustrator and I noticed that when I am working on both (either at the same time, or with one program closed) I sometime get the message in Illustrator "Not enough memory" or "Not enough ram" or when I am saving an image for web and devices "an unknown error has occurred"

BUT if I use Illustrator and Photoshop CS3 (for both) on Vista via bootcamp none of these errors occur.

I just don't want to imaging what will happen when I use CS4.

Is this due to the way Leopard is setup?

I am also looking to upgrade...So do you guys think the new macbook or macbook pros would be better? I mean, my current macbook is holding up well...but I just hate these errors. I prefer to work in Leopard than Vista.

Hoping to buy both an iMac and Macbook or a Macbook Pro when Snow Leopard comes out.

It hasn't slowed down that much. I do keep a lot of data (probably about 25b gigs worth.)

I turn off my computer about everyday.

The files that I do work on are less than 200kb. They are just simple vectors that I drew up.

I can never open up .jpg images in illustrator either.

I do however, keep all of my data in a separate partition. I set up 3 partitions (Leopard, Data, Vista). Is this possibly the reason why?

If anything I thought that this kind of set up would increase the speed of Leopard since only programs are the only thing on the Leopard partition.

No programs are running when I boot up the computer. Out of 50 gigs on the Leopard partition, 20 gigs is used. And that is for only for Leopard and its programs.