[CentOS] USB DVD drive disappearing during kickstart install.

Hi folks.

I maintain a bunch of centos based machines that are built using a 
somewhat stripped down (limited number but mainly stock rpms) centos 
distro.  The installation process is plain anaconda stuff with a 
kickstart file on the root of the DVD/iso.   The current hardware and 
media i'm using is DVD based.

On machines that have internal DVD drives (all IDE CD/DVD drives), 
everything is fine.  However, I'm having a problem that started in 4.6 
and continues in 4.7 on machines that don't have an internal DVD drive 
and therefore i must use a USB DVD drive.  On these machines, everything 
goes ok in the beginning.  The DVD is "seen" by the machine and boots 
fine, the isolinux screen comes up and i let the timeout go or i hit 
return to continue.  Then, almost immediately thereafter, (when i should 
see the blue screen with text about loading drivers) i see the blue 
screen with the prompt for language.  This is supposed to be a kickstart 
install, so at this point i know i'm hosed. 

If I use alt-f3 or alt-f4 (can't remember which one), i can see an error 
message saying that the usb-storage driver is loaded, but it cannot find 
any USB storage devices to read from. 

If i alt-f1 back to the main blue screen with the language prompt, i can 
go through the prompts for language, keyboard, however when i get to 
"install type", and select "usb cdrom" (i can't remember the text 
exactly...the machines are in the server room, and i'm at my desk ATM), 
it fails again.  I can alt-f3 back to see that the same error about 
loading the usb-storage driver was successful but it can't find any 
attached usb storage device.  Unfortunately, at this point, there's no 
shell yet available in alt-f2, so i can't poke around much).

It seems like somehow, something is happening like the USB bus is being 
reset and it's "loosing" the usb devices and they can't be found anymore. 

Note that the original boot occurred of the DVD drive (i got past the 
isolinux screen), so it's at least working in the beginning to get that 
far. 

I had seen this problem occur a handful of times in the past in my same 
distro based on CentOS-4.5, however it was sporadic and was usually 
solved by changing the manufacturer of DVD drive (i thought it was a 
hardware vendor not implementing the USB spec properly since most 
devices worked...only a handful didn't).  However, since moving to 4.6 
and also in 4.7, this problem is completely repeatable with all USB DVD 
drives i have (granted it's only 3 different vendors/models, but they 
all don't work, whereas all 3 of these used to work in the 4.5 based 
distro).

Also, as i stated earlier, on machines with internal DVD drives (IDE 
based), everything works fine. 

Has anyone seen anything like this?  Do you have any suggestions to try? 

One thing i'm going to try is downloading the stock  4.7 DVD ISO and see 
if it fails.  The download is taking a while, so i won't be able to 
report back on that test until tomorrow. 

Oh yeah, the machines i'm using that are having this problem are a Dell 
R200, Supermicro PDSMi, and Supermicro P4SC8.  I don't have the DVD 
drive mfg and model numbers handy, i'll get those as well.

Any help would be greatly appreciated. 

Thanks.

...alex...