Howdy all! I'm experiencing a similar problem. Essentially it went like this:
My Xbox is hard-modded with an Executer chip. I set up XBMC a year or so ago. Life was good.
Well, the wife asked why it couldn't just boot directly into XBMC since I never play games on it anymore. I said, good idea, looked up how to do it. I followed the instructions here:
XBMC install instructionsI ftp'd into the Xbox just fine. Since I was in there, I downloaded and copied over the latest version of XBMC.
I then went about uploading the new xbe file. I made the changes on my PC as directed in the link. I thought it a good idea (apparently I was wrong), to make a copy of the original evoxdash.xbe file. So I renamed it evoxdash.old. I was then going to load the 'new' evoxdash.xbe' file over the FTP. Apparently, renaming the file caused the FTP to stop working. I was completely unable to connect via FTP after that.
When I rebooted the XBox, I now see the MS dashboard. So, I looked up how to re-install the Evox dashboard. Seems like everyone says to burn an iso of the evox files on a disc, boot from it, connect by FTP, and copy over the correct files, and it will be fixed.
Only thing is, I can't get a burned disc to work with the Xbox now! I'm wondering if I am doing something wrong with either how I am burning or how I created the iso.
I've tried the following media and failed:
memorex CD-RW (12x 700MB)
maxell DVD-R 4.7GB (16x)
Sony DVD-R
Digital Research CD-r (16x) (I know CD-R don't generally work, but I figured, what the heck)
memorex DVD+RDL (8x)
I have some Verbatim DVD+RDL that I haven't tried yet, but I only have a couple so I figured I'd check first before I just make more frisbees.
I used Nero (express 6) to burn the CD-RW, but it would not let me burn the image to a DVD-R, saying it was the wrong format or something like that and needed a CD-R or CD-RW. So I used Power2Go for the DVD's. I did the CD-RW with both.
Thre weren't many options in xiso, so I'm not sure how I could have screwed that piece of it up, however, the file is only 2.44MB, so I don't know if that is correct. (It does appear to have all the files in it for Evox though).
So anyway, my question is:
1) Any ideas on why I can't get any of these discs to play
2) If not, is there another way of getting the the new dashboard on? I don't mind taking the hard drive out, but it seems that in order to get it viewable on my PC, I'd need to unlock it first, which I need the new dashboard for.
My last resort has been that when I modded my XBox the first time, I backed up the entire XBox hard drive onto one of my extra drives. I was thinking of upgrading the drive in the XBox anyway, using a spare 100GB I have. So I'm wondering if I could just use that backup, set it up the way I want, then install it. and go from there. That sounds far to easy though!

Thanks for your help.