Attached Prims are turning invisbible

Have you had this happen too? For the last while I've notice my prims and other avatar prims are turning invisible depending on how you move the camera. Most noteable is hair turning invisible then reappearing if you keep moving the camera. I have tried playing with the SL graphic settings as well as my video card setting and nothing helps. It's another SL problem. I'm not sure but I think it started with this last viewer I finally updated to: Second Life 1.21.6 (99587) Oct 14 2008 17:42:25 (Second Life Release).
It makes it pretty difficult to edit attachments if they keep turning invisible.

Also I noticed some AVi's are invisible and their attachments are visible, but gray. All the prims are in one place, but the boots or shoes are some where ahead of where the rest of the prims are. Only until the AV fully rezzes does everything come together. The AVi rezzing cloud is not visible either.

It's a known glitch, introduced with one of the recent client updates. Particularly annoying if you have a non-Human avatar like a Furry, and it's your whole HEAD that keeps disappearing!

Bear with it for now, and it should get fixed in a future client release. the only work-around now is to move your camera to a different position.

If you're referring to the glitch where this happens when you are sitting on a poseball or pose stand, it's fixed in the 1.22 Release Candidate.