Try using URLencodedFormat to change the URL string before
sending it along.
Placing them in quotes may help as well.
The other alternative is to use POST instead of GET if this
is from processing a form.
The problem is that the ampersand (&) is a variable
joiner in a URL, so when you pass it as you have shown above, the
action page and browser see only the variable definition before the
ampersand as one variable, and the data following that ampersand as
a different variable which happens to be empty.