Lately, we upgraded the ie browser to IE7 and unfortunately a critical application that we are running now displays quite frequently the error message: document.getelementbyid(...) is null or not an object.

Basically, upon trying to submit the values entered a form without any delay this error always occurs. But we have noticed that if the page is loaded and the information is entered and submitted after ~15min, no error occurs.

I think it isn't a code problem since it works under the above circumstances. Could it be a resource problem? If yes then which resource could it be?
Thanks in advance,