Hi, those of you who are more experienced with CE will no doubt get a good giggle out of this, however, I'm desperate for help.
I'm a bit of a novice and I was experimenting with custom ui's. I noticed that some ui's had the 'campaign' option and was wondering how you play campaign on ce. So the experimentation began. This is where it gets embarrassing. I copy and pasted campaign maps from normal Halo and put them in the CE map folder, including the bitmaps and sound file. After I discovered that this wasn't a good idea (ui screen was mostly black) I deleted the folders that I transferred. However, this didn't fix the issue. So, I uninstalled CE and reinstalled, but I still got the black screen. I uninstalled Halo and CE and reinstalled but still got the black screen. I tried a custom ui and this is the result:
http://www.xfire.com/video/384145/
I've been told that the bitmaps are corrupted, so again I uninstalled, made sure to delete all CE files and reinstalled but it still has the same issue, a very dark, mostly black screen on the default ui and strange colours on the custom ui as can be seen in the video.
I did discover however that if I run CE by right mouse clicking and selecting 'run as administrator' CE will run perfectly. But if I just double click on the icon the issue of the dark screen and strange colours occurs.
I'm guessing that there is a corrupted file somewhere still stored on my computer that runs as default when I double click on the CE icon, but then doesn't run when I run as administrator, I have no idea.
Any help would be greatly appreciated!! Thank you.
And this is my first post, nice to meet you all and to all those creating maps and tags and so forth, love your work :)

simple fix i had the same crap
you are ethjer running windows 7 or windows vista
right? yes i know you are lol
well if your getting into major modding or map editing i recommend you use windows XP
less buggy and doesnt use that stupid admin crap
to fix your maps
go into your halo ce maps folder
look at the top of the windows you should see a thing called compatiblty files
click it
it will show you all the files youve edited with a program that wasnt run as admin
if you delete these files it will be normal
the reson when you run it as admin it works fine is because it nullfies those maps when running a app in admin mode
like i said before switch to windows xp or when you run apps make sure its in admin mode
i hope this helped and i typed it fast so it may look like crap

Gamecheat!! Your a champion!!
It was exactly as you said, I clicked 'Compatibility Files' and there it was, the corrupted 'bitmaps' file. Unbelievable, it was something so simple but I would never had found it!
Thank you so much!! :)

yea i had the same problem when i used windows vista
i hated it thats why i use windows xp now

Not necessarily. I and many other prominent map makers use Vista or 7.