You may be aware of this already but just in case there are those out there who might benefit:

When creating an if statement that references a unselected dropdown list you need to use "-Select-" for Firefox/Chrome and "" for IE.

Easy workaround is of course to do the following:

else if (((input.Report_Type  ==  "Slotting Graph")  &&  (input.Region  !=  ""))  &&  (input.Region  !=  "-Select-"))

where Region is your dropdown list.

It is not necessary but it would be interesting to know why this is the case from the good/brilliant people at Zoho.

Thanks for a great solution that has made my full time job much simpler.