ESXi 5.1: can't mount .iso files more than 3GB to Windows VMs

Hello.

I do have one server with ESXi 5.0 and another server with ESXi 5.1. Both used for Windows based VMs.

When I mount .iso file on ESXi 5.1 VM with size more than 3GB VM can't see it (no disk in the drive).

VM on the server with ESXi 5.0 can see the same .iso file.

I've tried several .iso files, files with size less than 3GB works fine.

I'm using .iso from Microsoft if it's matters.

Are there any limits for the .iso size in the ESXi 5.1 or any settings to change it?

Thanks.