Hi Jules,
I have had a hard time to catch this one, but the gcc asm for blendRectRGB in juce_LowLevelGraphicsSoftwareRenderer.cpp is not consistent with its clobber list. it is modifying the %ebx register. Which is afterwards causing all sorts of very strange problems !
I suggest that you add a “push %%ebx” at the beginning of the gcc asm sequence and a “pop %%ebx” at the end (gcc does not want %ebx in the clobber list as it is reserved for the PIC relocation)