Windows 8.1 X64 Can't allocate more than 3584 MB to any guest OS,

[c0mputerguy72]

When running any guest with above 3584 MB allocated I receive the following error. This has been tested on multiple machines with different installs and is not machine specific.
Error received:

"Failed to open a session for the virtual machine WIN701.
VT-x is disabled in the BIOS. (VERR_VMX_MSR_VMXON_DISABLED).
Result Code: E_FAIL (0x80004005)
Component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}"

When I allocate below 3585 MB the guest Boots.
VT-x has been confirmed to be enabled in the BIOS.

System Info from Virtual Box Log:

00:00:00.001995 main Build Type: release
00:00:00.001995 main OS Product: Windows 8
00:00:00.001995 main OS Release: 6.2.9200
00:00:00.001995 main OS Service Pack:
00:00:00.017016 main DMI Product Name: 4318CTO
00:00:00.023970 main DMI Product Version: ThinkPad W510
00:00:00.023970 main Host RAM: 16315MB total, 13280MB available
00:00:00.023970 main Executable: C:\Program Files\Oracle\VirtualBox\VBoxSVC.exe
00:00:00.023970 main Process ID: 6512
00:00:00.023970 main Package type: WINDOWS_64BITS_GENERIC