Do you mean like a stomach ache? Definitely a lot of people find that their system doesn't take kindly to a lot of young sheng. The particular tea seems to matter somewhat too. I wouldn't say that it's a hard and fast rule never to drink it, but I think it's a good rule to listen to your body - if a particular tea or type of tea doesn't agree with you, you should probably avoid it. Personally, I don't drink that stuff (dry-stored young sheng) very often or in large quantities. Other people do and seem to have no problems with it. Definitely avoid drinking young sheng on an empty stomach if possible. If this is all with one tea (sounds like it is), you might also want to just try a different tea.
There are some TCM considerations - I believe the best explanation I've heard is that it's very, very cold qi (more so than normal green tea). There was a good discussion about it on the Livejournal community, which featured some comments by someone who knows a lot more about this than I do, but last time I looked for it, I couldn't find it.
I would try some other types of puer (some well-stored aged (>15 years) sheng if you can afford some small samples, some decent shu with a couple of years on it, and maybe some 5-10 year old sheng with a little more wet / humid storage) -- all of these will likely be mellower and earthier than what you tried, and also easier on your system.