Problem with PayPal when using IE8

We are using Zen Cart v.1.3.8 along with Website Payments Pro.
In IE8 when customers check out with Pay Pal and Pay Pal Express, they are taken to the Pay Pal log in page, asked to review info and click continue, then instead of an order conformation or being shown step 2 in the check out process, they are shown our log in page with no record of their cart. The check out process works as it should in all other browsers I have tried. IE8 in compatibilty mode, Firefox, Chrome, Safari all work fine. Any help as to where to look for the error would be appreciated. Let me know if more info is needed.

I believe I have fixed the problem. I changed the "check user agent" setting to off. My assumption was that Zen Cart did not recognize ie8 as a valid user agent. Is this valid logic?

As with all of the settings in Admin->Configuration->Sessions, leaving settings at their default settings is the best choice unless you have a clear specific reason for doing otherwise.

There is almost no reason to ever turn the "check user agent" option on. Changing that and other settings in that screen almost always causes undesirable results.

joebadd:

I believe I have fixed the problem. I changed the "check user agent" setting to off. My assumption was that Zen Cart did not recognize ie8 as a valid user agent. Is this valid logic?

Where do i find this 'check user agent' setting?