It means one machine has the latest windows updates and the other one does not, and your page exceeds the new limit of 1000 form elements. The cause is a recent ASP.NET security update and a workaround is discussed on this thread.
Note that the hidden field sused for viewstate may be a significant factor in the number of form elements so setting EnableViewState="false" on any controls that don't need it may help.
Hope that helps,
Joe