My server crashes a lot..Can I prevent this?

I recently started a server in January. It was running ok on my desktop, but my desktop was constantly being used. I got a laptop that I would only use to run the server. Everything was ok for about 2 weeks, then the server started crashing, people were leaving because of the 'endofstream' thing, and the server is usually really laggy now.

I looked at the CPU usage, and it stays around 50-60%.
My laptop:

AMD E-300 APU with Radeon HD Graphics 1.30 GHz
RAM: 4.00 GB
64-bit Operating System, x64- based processor
(HP with windows 8, if that has anything to do with it)

I use 3 GB of RAM for the server

I have a fan/cooler thing(I can't remember what it's called at the moment) that I keep my laptop on so it doesn't over heat.

The plugins I have:
ColorMe
Essentials
Factions
iConemy
marriage
mcMMO
Multiverse Core
Multiverse Inventories
Multiverse Portals
Permissionsex
PlayerHeads
PlotMe
PluginMetrics
SurvivalGames
WorldEdit

I made sure all of the plugins are updated, and I'm using the latest development build of craftbukkit.

When the server crashes, everything freezes, then everyone loses connection(EndOfStream). The are "warning: cant keep up" messages in the console.

Is there a way I can keep the server from crashing?