I don't think there is a lot of problem with that issue. Even if you've ticked the improvement block, you still are eligible for JEE 2010 & claim a seat if you get selected.
Moreover, if you get qualify in the exam, you'll be called for counseling first. There you'll be asked to enter the same details again. You can correct the errata there.
Still, to remain on the safer side, I suggest you to write an application to Chairman, JEE of your IIT zone stating the complete problem & the correct details. They'll surely look into it.
Please feel free to post as many doubts on our discussion forum as you can. If you find any question
Difficult to understand - post it here and we will get you the answer and detailed solution very quickly. We
are all IITians and here to help you in your IIT JEE preparation.
All the best !!!