Yeah, it's a lack of ram issue when the client crashes immediately like that. If you don't have the option to allocate more than 1GB of ram, you need to update your Java to the latest version (preferably 64bit if you're able) and then make sure your Java settings in the launcher settings is set to the right version of Java. Then you should be able to allocate as much ram as you want.
I do 3GB for modpacks with heavier mods. It's just a target max though, not really a hard max. Java doesn't seem to care about how much ram you want it eating.