Upload the .img driver to NFS server, and boot by RHEL CD,
Code:
linux dd=nfs:server.mydomain.com:/directory/drivers.img
http and ftp also are supported.
However, I do not know whether the following command would fix your issue:
Code:
linux dd=hd:sdx:/home/drivers.img
sdx represents removable usb driver. Say again, I'm NOT sure of this solution, but you could try and I'm very pleasure to hear the result.
Good luck.
Phillip