I have created a static library in Iphone SDK in which I used some UIDevice properties. When I run the app, this xcode show this error UIDevice Undeclared... Even the same code is running perfectly fine while I don't create static libraries and just build the source files.
Have you tried adding
#import <UIKit/UIKit.h>
...to the top of your class .h file? I was running into similar problems as you are having, but when I added that import into my .h files that seemed to fix a lot of the errors.
Hope that helps.
Andy