URL has null varialbes & pagerank but no google cache

follow up to http://www.webmasterworld.com/forum30/33134.htm

[jonahviakeyboard]

This is a two question follow up to another thread: [webmasterworld.com...]

I'm also seeing an address that is PR3, but has no Google cache.

The case I'm seeing is a dynamic address for site search results with lots of undefined variables, such as www.example.com/sitesearch.php?ex1=&ex2=search+term&ex3=

If I remove some of the undefined variables, the PR shows as 0 and there is still no cache.

Question 1: What is causing this?

Question 2: What is the best way of handling site search results URLs?

All three variables don't have to be declared to get a site search result, as would be the case with non-essential fields like city, state, or price range. Froogle doesn't declare variables in the URL unless the user specifies (as with Bands or Price), which would seem to be a good example of how to do this. But given that I have site search results with existing PR (but no cache), should I scrap the way it works and start over following Froogle's format?

Thanks for the help.