In general . . .
I hope you'll continue to contribute to this discussion of universals!
. . . I'll participate when I can but I probably won't be back online until at least Monday (my Internet connection on my other machine has recently become, um, suboptimal).
Here are the bare bones, for the benefit of anyone who could use a little background.
According to the standard philosophical definition, a universal is any characteristic, property, quality, or what have you, or a complex of such properties, that can occur identically in more than one context. (You may encounter the definition 'repeatable predicable', meaning a property that can be repeatedly predicated of more than one object.) If there is an identical 'man-ness' among men, then 'man-ness' is a universal; otherwise not. (I think not.) If a specific shade of green can occur identically in two different conscious experiences, it's a universal; otherwise not. (I think it is.) If the number pi can occur identically in more than one context, it's a universal; otherwise not. (I think it is.)
The problem of universals, in a nutshell, is whether there are any real universals at all, and if not, why we 'think' as though there are.
The two logical possibilites are realism (the view that there is at least one real universal) and nominalism (the view that there aren't any real universals at all).
'Nominalism' gets its name from medieval disputes over the problem, in which one view (most famously propounded by William of Ockham) was that 'universal concepts' were really just names for ranges of nonidentical objects. Today most philosophers probably wouldn't use it quite that restrictively, so we'd regard conceptualism (the view that apparent universals are really just concepts, not really-out-there objects) as a form of nominalism, not as an alternative to it.
Please note that a 'realist' is not committed to the view that anything we think is a universal really is one. For example, there may be lots of proposed universals -- I'd list 'man-ness' here -- that turn out on inspection to represent not a single identical property but a (possibly ill-defined) range of distinct properties or complexes thereof. Denying that these are universals doesn't make you a 'nominalist'; as long as you acknowledge at least one real universal, you're a 'realist'.
There are several varieties of 'realism' that I'm not going to try to sort out here. There are 'realists' who (like Aristotle) tend to think that universals don't exist 'on their own' but only 'in' particulars; these realists might also deny that universals exist in any 'eternal' or 'timeless' way. The more Platonistic ones will claim that at least some (not necessarily all) universals are self-existent and timeless. But those are subsidiary issues.