Without the logs, I can't indeed diagnose the issue...
Common causes for avatar rezzing failures are:
- A failure to create the initial bake (or a corrupted baked texture server-side).
- Missing mandatory body part (your avatar must always wear exactly one shape, one skin, one pair of eyes, one hair).
- "Missing" body part asset: this may happen if your inventory or its cached list got corrupted, or when SL's assets server got troubles or lags. Note that when encountering a missing body part asset, the viewer normally reports it via a notification after it failed to rez it.
To fix the above problems, perform the following actions (in the given order):
- Rebake your avatar textures by pressing CTRL ALT R.
- Check that all four mandatory body parts are worn (open your inventory, select the "Worn Items" tab and check that a shape, a skin, eyes and hair are worn).
- Try wearing another full avatar (right click on a folder containing a shape, a skin, eyes and hair, and select "Replace Outfit" in the context menu).
- Clear your cache and relog to clear a potentially corrupted inventory list cache.
If all the above fail, you are faced with an asset server issue and I'm afraid no viewer can do anything about it.