Iam having the same issue..... my avatar will constantly be a partical cloud, one thing works for me.... but then makes me so laggy that i just give up and log out. i have been having this problem for a few days, i honestly think its a sl issue because my alt account is perfectly normal.
what i do is.... advanced settings.... character.... then reload ( can't quite remember what its called) it rezzes my avatar.. but makes me super lagg afterwards :-/