Hello,
Could you please provide us with more information in order we could deduce some solution?
Firstly, what version of Kentico
CMS are you running? Do you have applied any hotfixes?
What particular form subscription are you using? I mean, what web part is being used in your case? Is it a standard BizForm or rather some custom user control/form?
As for the issue you are experiencing - are there any error messages? If so, please upload here some screenshots. Thank you in advance.
By any chance, is it possible for us to test it directly on your site?
Just a brief though, don't you use any add-ons in your IE7 browser? Please try to disable them or test it on another computer.
Are there any JavaScript web parts/controls on the page? It's possible they may interfere with each other. Please try to put your form to the blank page and test it over there.
Best regards
Ondrej Vasil