If you can't or won't wait for the chlorine dioxide pills to do their job (those cysts are hard to kill!), I strongly recommend using another method. Giardia cysts are less resistant to chemicals than cryptosporidium cysts, but not much. There is a good reason for those long wait times, as you've recently discovered the hard way. See Jeremy's link just above.
Not all filters are heavy and clunky. My homemade gravity filter (using a Katadyn Hiker Pro replacement filter and vaguely based on the now defunct ULA Amigo Pro) weighs 6.6 ounces, which is far less than the weight of an extra liter of water undergoing chemical disinfection. During a 5-minute break I can filter a liter of water, drink half of it, and carry only the other half liter. The water tastes better, too! Of course this weight comparison is valid only where there are frequent water sources, but that's mostly the case where I backpack. If you normally go all or most of the day without water sources and have to carry two liters anyway, the weight advantage of course goes to the chemicals.
For more info on various MYOG gravity filters, go here--there are several versions:
Mine is the one that starts well down on page 2, in the post by Cola Vaughan. (Cola, if you're reading this, thank you!) No moving parts to break and no pumping.
I haven't used the Sawyer squeeze filter but have heard good things about it. It weighs half as much as my gravity filter system, so I plan to check it out.