At the risk of being bombarded with questions or differing points of view:
Here's a suggestion which may get you out of a PayPal mess - turn off the automatic redirects for the module. If you use any payment handler where your customer is sent away from teh site, and then returns, and the URL they return to is NOT an SEO URL, then the SEO script redirects them to the corrected URL, which can cause a few problems with posted data.
Secondly, if you are using the EzPages module, and you place the content for the pages in the EzPages content box, as opposed to creating links to other internal pages, then the SEO will always place chater=x&id=y tags at the end of teh urls. A solution to this to add extra pages the long way, where you actually add the pages to the core Zen Cart code, rather than using EzPages. The pages can then be called anything you like, and this will appear in teh URL. For advice on how to do this, check out the about us contribution in the downloads section.
The advantage of adding the pages the long way is they are also multilingual, and they are accessible using the SEO URLs automaitcally.
Good luck
Absolute