IPhone OpenGL swapBuffers problem! Help!

Question

Hi guys,
I am writing a 2D game using OpenGL, based heavily on Apple's CrashLanding sample.
My main game loop calls three functions:
1. update, which moves all my objects
2. draw, which draws the objects to the current OpenGL context using Apple's Texture2D
3. finally, the swapBuffers function provided by apple.
I've set the rendering timer to 60 FPS. Right now all I'm drawing is a background texture (320x480 - fills the screen) and 10 or so clouds, about 100x50 px each, with blending enabled.
**Here's the problem: most of the time it runs fine, but seemingly at random, about every tenth frame or so, the swapBuffers function takes 10x as long as usual (about 0.002 sec. instead of 0.0002 sec) - Does anyone know what could be causing this? If I understand correctly, it seems like any slowdown should come in the draw function, and the speed of swapbuffers should be completely independent of what's on the buffers being swapped, right?
Anyone know what could be causing this or seen anything similar?

Answer 1

Yea I noticed it because there are a few really choppy frames every 2-3 seconds but it's smooth as silk the rest of the time, even though (seemingly) nothing changes.
I had one thought though: In the process of moving my objects around, I allocate and then release a lot of Vector2D's (a class I wrote). Is there any way that the de-allocated vectors pile up and the stutter is when it decides to clean them out?
When I run the Object Allocations instrument, the "Net" number of Vector2D's stays steady, so I don't think I'm leaking anything. However, the big red bar to the side of that is huge, though mostly light pink with a tiny sliver of dark red. What does that mean? Sorry for all the newbie questions
Thanks a ton!