Page cannot be displayed error with Paypal IPN

We have implmented Zencart version 1.371 with IPN. While Paypal IPN orders are going through, many customers are getting a page cannot be displayed error (with a retry button) when they click the confirm the order button on the checkout confirmation page (which leads them to https://www.paypal.com/cgi-bin/webscr). What can we do to fix this?

Can you trigger this situation on-demand?
Have you checked your server's errorlog for any details about the cause?
You will probably have to report the issue to PayPal, since it's their server that your customers are trying to reach at that point.

Hi,

Thanks for your reply.

Can you trigger this situation on-demand?
No. I've tried testing on 3 different machines (Windows XP, WIndows Vista, WIndows 2003 Server) and have tried both Firefox and IE. I cannot replicate the issue myself. However, many users have reported this issue, it seems to happen about 25% of the time. One user did tell us it was working for them before. So not sure if this is a sporadic issue.

Have you checked your server's errorlog for any details about the cause?
We've checked the Apache error logs and don't see anything. Any other logs you suggest to check?

You will probably have to report the issue to PayPal, since it's their server that >your customers are trying to reach at that point.
That's been done.

Any ideas?

Hello, I have had a similar problem with paypal and took some effort before finally fixing the problem. Some how there was a trojan of some sort that anivirus and other programs did not pick up on that was causing the problem. It was redirecting all paypal traffic from my pc...and I was getting "page cannot be displayed". "Spybot search and destroy" is what finally did the trick. I downloaded it for free from Cnet's download.com... hope this helps.

Hi Nasado,

I appreciate your response, but I doubt its a Trojan. Keep in mind this issue is not happening on nay of the mahcines I tested and is only happening on some users computers. If it happened on 1 or 2 clients machines, then your virus hypothesis could be true. But to happen to many users (at least 2 a day) would mean they all have viruses which I would seriously doubt.