Are you referring to the Multiple Ring Buffer (Analysis) GP tool? I just ran a quick test with this tool and was able to create about 30 buffers around a point successfully. What is the tool and workflow that you are using?
My work flow is as in the "Creating buffers for the vignette" section.
When i create a multiple ring buffer with 18 rings at 0.5km apart it works fine.
[ATTACH=CONFIG]12512[/ATTACH]
However when I create a multiple ring buffer with 24 rings at 0.5km apart i get the following result, i.e. one of the buffers is 1km apart instead of 0.5km
Thanks for the link. I tried using this wizard with 24 rings and it works for me. Does it seem to happen with other shapefiles/feature classes or is it specific to this one? I'd recommend you try on another shapefile. Also, if you haven't already, you may want to install Service Pack 4.