Thanks to Guillaume from TPG for pointing this out, and for Rob for digging out the answer. Our cumulative update for August was considerably smaller than the one for June. How come? Its cumulative isn’t it? Doesn’t it just get bigger? Well the change that happened with the August release – and all future Project Server 2007 and MOSS 2007 cumulative updates is that they require SP2. Another way this requirement may show up is if you try to load the CU and then you get a message saying “There are no products affected by this package installed on this system”. This could mean you have loaded previous CUs, but haven’t yet loaded SP2.
Another reason you may get this is if you are trying to install the x86 version of a CU and you actually have the x64 product installed. So check carefully.