VMware ESX Total RAM Capacity less than physical

You have 5906MB of total Memory capacity for VM's.

You have 4608MB of reserved Memory capacity for VM's.

You have 1298Mb of available Memory capacity for VM's.

You don't have enough available Memory capacity to run a VM with 2GB of RAM.

You'll need to adjust your memory reservations in order to make enough memory available for the new VM.

The physical memory shown on the Configuration tab and the memory capacity shown on the Resource Allocation tab are two different things.

The memory shown on the Configuration tab is the amount of physical memory in the host.

The memory shown on the Resource Allocation tab is the amount of memory that is available to virtual machines. Your problem is that you don't have enough memory available to virtual machines to run a 2GB VM.

Why the physical memory and the available VM memory are so different is beyond me.

Look at your virtual machines. If you have specific RAM reservations, that means you're ensuring that the virtual machines have that RAM available to them. If you plan to oversubscribe or make the best use of your resources, you probably don't want the RAM reservations defined.

Edit:

Check your hardware. If this is a multiple-CPU system, make sure your RAM is balanced across nodes. Then...

Update your ESXi installation.

You're currently running VMware ESXi 4.1 build 260247 from June 13, 2010!!!

The current build of ESXi 4.1 is Build 988178 from January 2013. You may be experiencing a bug.