I had this same problem when running Minecraft with recent versions of Forge on my netbook (vanilla runs fine.)
How I worked around it:
I set the minimum memory requirements for java to 256M (from 512M) to allow a little more system memory left over for my weak video card to use for whatever Forge is now doing differently at start up (I think LexManos made a comment about it swapping textures.)
In MultiMC I do this by clicking "Instance Settings" button, "Java" tab, and changing minimum memory allocation from 512 to 256.
From the command line (with a shortcut) you would make this change by calling java.exe with -Xms256m instead of -Xms512m.
My better solution is to just run minecraft from my desktop, but I don't always have that with me.