Looking at the memory usage for my game is stays around 65mb on this one specific frame, barely anything.
Randomly I'll get huge framerate drops while testing random things, like the game completely slows down. Sometimes refocusing the game (clicking somewhere on the game's screen) will get rid of it, sometimes it doesn't. Memory usage doesn't spike at all during this.
So I ran the profiler that comes with 2.5+, what spikes is "Display"... now that info isn't really helpful to me since it's so vague.
During the frame drops I'm not doing anything super specific, usually just walking around the level.
I use the Active System Box to display text sometimes when walking over specific Actives on the map; this will sometimes trigger it about 10% of the time I activate them. The events that display text are set to run only once, again memory usage doesn't go up at all.
I'll put pics of the profilers below.
Session with frame drops:
Frame runs fine: