One aspect of experimental science that never shows up on TV procedurals (NCIS, CSI) is the "lab mystery" - the simple procedure that's supposed to be a piece of cake, but turns out to be unnecessarily and surprisingly complicated. Here's an example. There's a material that is supposed to be photopolymerizable; it starts out as a liquid monomer, and under UV exposure it's supposed to polymerize into a gel. We have some, and we also have a UV lamp. As a simple test, we exposed the monomer to the UV for tens of minutes - no response. I'm sure we'll figure this out, but this sort of thing never happens to Abby or the guys from Mythbusters.... Feel free to leave other examples of lab mysteries in the comments.
update: Mystery resolved. In this case, the answer seems to be "more power". A much (~ 20x) brighter UV lamp works quite well. The paper we're working from didn't really mention intensities, so I think we can be forgiven.