We've had multiple discussions about this here before.
Some world-wide electronics group I can't remember the name of decided that lead in discarded electronic equipment (solder with lead in it) was unacceptable. So. Completely ignoring the massive number of very extensive and expensive studies that were done 40-50 years ago, buy engineers and scientists who are retired now; it was decided to eliminate lead in solder by manufacturers (through laws).
Those old studies were done to find out why 'tin whiskers' were forming and shorting-out the newest low-voltage circuitry being developed in micro-electronics. It was determined that high-content tin solder in use at the time wasn't a factor in most electronics at the time because the currents were so high in most circuits that when tin whiskers formed, they were immediately blown-up when they formed a bridge to another contact point because of the current involved. The introduction of low-current circuitry showed the 'tin whiskers' to be a problem, and the studies determined that the introduction of lead in the tin solder, reduced tin whisker formation. If you've ever seen the old balls of very fine 'dust' in 1960's 1970's era television sets, that wasn't dust, it was balls of tin-whiskers.
Anyhow, kellys_eye is right on target about why lead was eliminated from today's manufacturing electronics, it was an eco-friendly, politically-correct decision. The rationale was determined to be acceptable because most of today's electronics for consumers is determined to be 3 years or less, and before tin whiskers start forming.
As Harld Kapp noted, there are exceptions to the new laws for critical circuits (not consumer oriented), that are expected to last much longer than 3 years without failing.
The first thing I'd ask Stese is if his soldering iron tip is clean. My experience with the problem he's having is that if the tip is not clean, it won't transfer enough heat to the solder to completely melt it, and all's you get are solder balls.
The second thing I'd say is that I too, have had old solder that just doesn't melt right anymore. I don't know the quality of the old solder you have, but I do notice that (while I don't know the right name for the chemical reaction) lead solder has a tendency to get some kind of 'oxyidized' film on it, especially if stored in humid conditions for long periods of time. I usually 'wet' a paper towel with rubbing alcohol and wipe the length of solder to get that dusty film off the solder to see if it'll melt right or not, and if not, I just toss the problem solder (Ooooo, make that 'recycle' it by the appropriate disposal method suggested by the laws in my area).