This sounded interesting, and I thought as a lay person, with some basic reference books, I could try to figure this out, myself.

So here's what I found out. (From: Webster's NewWorld STEADMAN'S CONCISE MEDICAL DICTIONARY) I'm sure I could have found these definitions off the web, but I had the book so I looked there, first.

Definition of Flocculate: To become flocculent. (Okay! another step!)

Definition of Flocculent: 1. Resembling tufts of cotton or wool; denoting a fluid, such as the urine, containing numerous shreds or fluffy particles of gray-white or white mucus or other material. 2. In bacteriology, denoting a fluid culture in which there are numerous colonies either floating in the fluid medium or loosely deposited at the bottom.

Definition of Serum: (plural.: serums or sera) 1. A clear watery fluid, especially that moistening surface of serous membranes, or exuded in inflammation of any of those membranes. 2. The fluid portion of the blood obtained after removal of the fibrin clot and blood cells; sometimes used as a synonym for antiserum or antitoxin.

So, in simple layman's terms:
Flocculates serum, means, it causes serum to get, well, looking like there is cotton or wool floating in it. So it 'mucks it up;' does not sound like it is a 'good thing.'

Now to the second part.

Definition of Precipitate: 1. To cause a substance in solution to separate as a solid. 2. A solid separated out from a solution to suspension; a floc or clump, such as that resulting from the mixture of a specific antigen and its antibody. 3. Punctate keratitis; a punctate opacity on the posterior surface of the cornea, arising from the inflammatory cells in the vitreous. (Doesn't sound like #3 applies here.)

So, in simple terms:
Precipitates serum proteins means, it causes the serum proteins to separate (I 'THINK') into separate solids. This doesn't sound like it's a good thing to have your serum proteins to do, either.

I hope this information is helpful to everyone. The thing I think Dr. D is trying to get us to do, (IMHO) is to be more self assertive, and look these things up, ourselves. Do some of our own research. To not expect every answer, be handed to us on a platter. Be inquisitive. Dig deeper, than just getting a simple answer.