Man, I just went back and tried the trade again on ESPN trade checker and once again, it failed. It has to be that Real GM is taking the Knicks trade exception into consideration and ESPN isn't. In any event, if the trade is possible, then I'd trade Jimmer straight up for Shumpert. The problem is, I thought the Knicks were looking for frontcourt help.
So it looks like ESPN is right and RealGM is wrong.
However, there is a way to make this trade work, if the Knicks are really into it. If we kick in Hamady N'Diaye and the Knicks kick in Cole Aldrich (both guys make the same amount, both unguaranteed), then the increase in total salary brings the 125% + 100K rule into play - we'd be clear by a whole $11K! But, those guys (Aldrich and N'Diaye) can't be traded until December 15th.