Macaroons are a bit of a bitch. Totally oven dependent as well, and just all round pain until you nail them.
Eggs work best if they're at room temp, and the whites even better if they've been out over night too. Did you do the resting before you ovened them? 30mins at least for the chance to form the skin on the top. What temps did you use in the oven? Recipes are crap for macs, as ovens differ so much, you have to play with yours.
You may well have over-whipped the eggs? gets to a point where they'll then get sloppier. Did you go French, Swiss or Italian meringue?