Help with an Exit Splash Code and Paypal buttons

Help on the following greatly appreciated:
I have an Exit Splash Code that when the visitor tries to close the page a window pops up inviting him to Cancel and Stay on the page to see a Reduced price offer. Then the person has to click on Continue to exit the page or Cancel to stay and see the new offer. The new offer page is an
exit.html file which opens together with the pop up window mentioned, supposedly making the index.php file to close. Only if the person clicks on Cancel, this new offer page remains.
I have a button with a Paypal code on that new offer page, but something weird happens: If the page is entered from the Exit Splash Window (by clicking on Cancel), the button takes you to a Paypal page that says that "The transaction could not be completed."
If you look at the url you are in before you click on the payment button, you see you are still in the index.php file and not in the exit.html file. The only way the Paypal code works with the button is when the exit.html is entered directly by typing the url, in this case, you enter the Paypal Payment page without errors.
The question is: what effect is causing the Exit Splash script that, instead of showing the url of the exit.html, it is showing the url of the index.php and causes the Paypal button not to work. It's like something in Paypal is thinking that the button is not the one that was coded in Paypal.
You can check all this by going to:
Closing the page Window through the X
Click on the Cancel button on the pop-up window (not the opt in window)
Then going to the payment button and clicking on it.
If on the other hand you type:

And click on the payment button
you are taken to the correct Paypal page

The code used is:
<!-- Start of ExitSplash.com Code -->
<script language="javascript">
var exitsplashmessage = '***************************************\n\n W A I T B E F O R E Y O U G O !\n\n CLICK THE *CANCEL* BUTTON RIGHT NOW\n TO STAY ON THE CURRENT PAGE.\n\n I HAVE SOMETHING VERY SPECIAL FOR YOU!\n\n***************************************';
var exitsplashpage = 'exit.html';
</script>
<script language="javascript" src="exitsplash.php?tc=3399cc&uh=none&ad=none&sh=n o&hv=no&bh=22&fs=12&lf=Arial&at="></script>
<!-- End of ExitSplash.com Code -->

I will be very grateful to anyone that can give me some help on how to make this button work properly.