Numeric value in URL causing problems with page PHP output

Hey all,

This one is a bit quirky. I have a search option via drop downs. All works well, except when one of the drop downs is a numeric value greater than 1 (so anything 2 or over causes problems).

When the page is rendered the following code shows no output on the page.

<?php echo $mainRecord["dealer_title"] ?>

If there are no numbers in the URL (a numeric 1 is fine as I mentioned), then the above code works fine.

This smells of a 'record number' issue, but no idea where to go from here.

Url examples as follows:

Works:
peugeot-scooters-list.php?model_range=Vivacity&engine_size=&cooling_system=&colours=&submit=Search

Fails:
peugeot-scooters-list.php?model_range=Speedfight+3&engine_size=&cooling_system=&colours=&submit=Search

I have tested the number theory with other fields and get consistent results.

On a side and possibly related note, I seem unable to get useSeoUrls' => True to work.

Thanks

Paul