Error while compiling

I tried to compile SDL 1.3 from subversion again. I compiled SDLmain
just fine, and I have the library file, unfortunately I can’t compile
SDL. I get these errors:

C:\MinGW\bin…\lib\gcc\mingw32\3.4.5\include\mmintrin.h||In function
_mm_packs_pi16':| C:\MinGW\bin\..\lib\gcc\mingw32\3.4.5\include\mmintrin.h|116|error: can't convert between vector values of different size| C:\MinGW\bin\..\lib\gcc\mingw32\3.4.5\include\mmintrin.h||In function_mm_packs_pi32’:expressionless:
C:\MinGW\bin…\lib\gcc\mingw32\3.4.5\include\mmintrin.h|131|error:
can’t convert between vector values of different size|
C:\MinGW\bin…\lib\gcc\mingw32\3.4.5\include\mmintrin.h||In function
_mm_packs_pu16':| C:\MinGW\bin\..\lib\gcc\mingw32\3.4.5\include\mmintrin.h|146|error: can't convert between vector values of different size| C:\MinGW\bin\..\lib\gcc\mingw32\3.4.5\include\mmintrin.h||In function_mm_unpackhi_pi8’:expressionless:
C:\MinGW\bin…\lib\gcc\mingw32\3.4.5\include\mmintrin.h|160|error:
can’t convert between vector values of different size|
…and many more, but they all look the same.
What’s going on? What does MMX have to do with it?