external class files?

[DCU]

I am attempting to create some classes for an aplication that I am
developing.
 The classes themselves work fine when they are included in the same file as
the rest of my code, but when I try to move them to a serperate file I get
the
following error:

illeagle use of precompiled header
SysEventMgr.h Line 189

I anybody has any ideas on what I am doing wrong please let me know.
Thanks,
Kristopher Keller