I have the Tivo Series 2 and the original Tivo stand-alone units (which ironically are also made by Philips) in the same room. I'm using the multi-Tivo remote feature which allows more than one Tivo to be controlled by the same remote sending slightly different codes to each. These multi-Tivo device codes all work fine on the TSU2000. It's got to be related to the slow IR on the hard buttons. I noticed one command took over a second before the Tivo responded.
I looked at the differences between the play code for the two different Tivo units. The codes are almost identical but for maybe three numbers: