I've encountered a really bizarre problem this morning. I've been using VS2005 for many years without any problems. This morning I needed to rebuild a library called gdk-pixbuf which I've built many times before. It contains a source file called gdk-pixbuf-animation.c

If I build my Release version with Link Time Code Generation enabled I'm suddenly seeing the following error message:-

fatal error C1047: The object or library file '.\Release\obj\gdk-pixbuf\gdk-pixbuf-animation.obj' was created with an older compiler than other objects; rebuild old objects and libraries
If I disable Link Time Code Generation I see this error instead:-

fatal error C1900: Il mismatch between 'P1' version '20060201' and 'P2' version '20050411'
I'm totally baffled. It only seems to affect this one project (and even then, only the Release build). I've even restored a backed-up version of the vcproj file but it's no different. Can anyone hazard a guess at what might be wrong?