I'm sorry for your lost points, guys. If it's a consolation for you, I spent two mornings completely puzzled with this issue, to the point I asked for help in the forums an lately, when I discovered the -subtle- question, felt it was worth to broadcast it all along.
Mi actual position is as developer. Some year ago I acted as DBA but then my company outsourced the SQL Server services and now we are using a hosting. I verified the code against SS2k and 2005, as stated in the question. I did not bother on service pack updates because I didn't think on that possibility.
The question, once isolated, was treated to focus the key point, that is, I had a SQL sentence with a line comment alone and the next line (valid SQL code) did not execute at all. It was no tricky code; only a damned line that did not want to run. I sent the code to my colleague, a very clever programmer, and he thought about examining the SQL text with an hex editor (it would not have crossed my mind in life), so he discovered the lacking character.
It's a very disturbing behavior, and, looking the answers, those of you who complain has the issue addressed with the correct update, but I have seen a lot more of readings without further comments, and I guess maybe there has been someone who has got the same answer.
Anyway, I admit it was a sure-you-lose-question. I apologize for this to all of you who have got disappointed, and by the other side, I hope it can help someone to avoid getting so confused as I got.