I don't think any standalone Internet Explorer updates have ever been released for Windows Mobile - you would have to update the entire OS, which is also not possible on most devices.
Most people who ask this question have encountered a web page that incorrectly concluded that PIE is incompatible with the site based on its version number (which doesn't correspond to the version numbers of the full IE, in terms of capability), causing the people to incorrectly conclude that an upgrade to PIE is what is needed to fix the problem. You may be able to fix it by using a third-party program to change PIE's user agent string, but otherwise you will have to get a different browser like Opera or NetFront.
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