This is an error I encountered when creating a custom search page in MOSS 2007.

After creating a new custom search page and placing the Core Search Results, Search Results Paging webparts I always had a Javascript error "Object Expected", line xxx when clicking on Next page. 
The line number corresponds the href of the paging link : javascript:PostToUrl(''). My first idea is that some basic required javascript library has not been loaded.

Luckilly I found someone with a similar problem, actually a different problem with the same solution: http://www.sharepointblogs.com/joeldhall/archive/2007/01/04/17470.aspx

In Joel's solution just adding the Search Box webpart and setting it to closed in order to hide it is sufficient. Unfortunately in my case this is not. If I close the web part the error reappears.

Maybe someone else knows why this happens and has a better solution?