OK!!! Fixed mine at least!
Bit of a faff, but used CCSMon to grab the EDID to a 'viewsonic' dat file, then used viewsonics own EDID tool to overwrite the pretty useless 1152*876@75 Hz mode to 1920 * 1080 @ 60Hz (You change 2 bytes)..
Then used powerstrip to 'update the EDID'.. turn monitor off/on, booted the 360 and hey presto! 1080p!
If you are feeling as brave as I am,
Download Softmccs..
http://www.entechtaiwan.com/lib/softmccs.shtm
and Power strip
http://www.entechtaiwan.com/util/ps.shtm
1. Open softmccs, it'll take a few seconds, it should show Viewsonic vx2825wm in the top drop down list..
2. File->Save EDID as..
3. Save as type 'Viewsonic EDID File', and save it to a file..
4. e-mail to me
I'll modify it, if it's as easy as mine, then e-mail it back
then..
5. In powerstrip->options->monitor information
6. The drop down bottom left, select "Update EDID", answer yes to the warning, open the (hopefully) returned EDID file, and it'll attempt to update it.
(I am not sure if you need a registered version of powerstrip to enable the 'update EDID', I bought it years ago to do my Toshiba LCD, so it's a fully registered version)
Of course, there is always a risk, but has worked for me.!