My home page has PR0, it used to have 4, but if I check the home page by putting http://www.urbanjungle.uk.com/index.asp in the address bar instead of just http://www.urbanjungle.uk.com It shows 4. Will this affect my position in the search eventually? It's just started happening over the last 2 weeks.
pr means naught to the consumer; but remember that all search engines are text based. therefore, http://www.urbanjungle.uk.com is indexed, as well as http://www.urbanjungle.uk.com/index.asp my point is try to be consistent in describing your site with internal and back links.
Ideally you wan't each page to have a unique URL, that way you won't be penalised for duplicate content. If G thinks http://www.urbanjungle.uk.com and http://www.urbanjungle.uk.com/index.asp are 2 distinct pages how will it know which one ranks higher, ideally IMO you want 1 high ranking page rather than 2 low ranking ones.