Hi there!
There are a couple reasons I could see that happening:
1. Version of the Ghost executable
Can you compare the version of the Ghost executables, as well as the architecture (x86/x64)? It may be that the PXE boot image is using a lower version. What version are you using, by the way?
2. Presence of storage driver
The PXE boot image may not have the latest storage driver, which can affect that showing up. You may need to recreate your PXE boot image.
3. Version of WinPE
Is the boot disk using a different version of WnPE than the boot USB?
Thank you,
Randall Newnham