Brake job blunder?

So I have a 2000 XE CC, when I got it the front driver-side brake caliper was leaking from the rubber around the piston, I had it replaced and it's been fine since. This evening I attempted to replace the brake pads on the truck, starting with the passenger side. No issues until I went to compress the caliper pistons back so that I could get it over the new pads. When I did, brake fluid began leaking out from the same place.

Is this just due to age?
Did I do something wrong?
Is it fixable without replacing the entire caliper?

I've never had this problem with any other vehicles I've owned. I couldn't find any threads in the search related to the 2000. Any info would be awesome.