SLC6, GCC 4.7, but got the same results on MacOS X 10.8 as well.
It seems that some new issue crept into v5-34-00-patches not too long ago. One of the custom converters that the ATLAS TF1 demonstrator code uses is not functional with v5-34-10 or v5-34-00-patches. But it works fine with v5-34-09. The custom converters are not broken on principle, I needed to extract the exact class from our code to demonstrate the issue. (Wasn't able to create the issue with much simpler classes.)
Attached is a code demonstrating the issue. fileWriter.cxx creates a branch using EventFormat_p1, and fileReader.cxx tries to read it back using edm::EventFormat. When compiling the code against v5-34-09, I get the output that I expect:
Info in <fileReader>: Opened the input file
Info in <fileReader>: Input tree accessed
1. element: Branch name: Test1, Class name: Bla1, Hash: 0x00000001
2. element: Branch name: Test2, Class name: Bla2, Hash: 0x00000002
But when I compile the code against v5-34-10 (or the head of the patch branch), the last two lines are not printed. I only looked at the converter a bit closer, it's obvious that my user code is never called for the conversion. But I have no idea why.
Custom converters are of course very central to the ATLAS developments, this is why I gave the issue such a serious priority. (As the EDM demonstrator is not functional with this latest ROOT version...)