Perhaps I was completely wrong - skip to the Mysid's comment. My sincere apologies then. But this explanation just doesn't work/compute in my head - even today finding MD5 collisions is extremely computationally expensive, yet the person says SHA1 + MD5 is only slightly more computationally expensive.
Let's put it in layman's terms: let's say your cluster made of a thousand GPUs finds MD5 collisions for given data every second. Now finding an SHA1 collision in Google's case required 9,223,372,036,854,775,808 computations based either on purely random data or data which needed to be fed to the SHA1 algorithm in succession both of which you cannot get using your already found MD5 collisions, because they are not random. I cannot see how your non random MD5 data could be used as a basis for cracking SHA-1 simultaneously. Again, maybe I'm totally wrong about that.
I'd also love to hear someone with a good cryptography background rather than believe a random person on the net or my amateurish logic.