Ah, this could be an HTTP failure then - as if some avatars were not displaying it may be that the page request went through OK and then subsequent calls to avatars failed.
Next week I'll run the IIS diagnostics toolkit and see if I can capture a crash happening to see what causes it
. It seems to happen once or twice a week for a few mins at a time - so it's nothing serious in server downtime terms (uptime is a touch over 99.9%), however I can imagine it must be a pain if you are in the middle of replying
! If this does happen after you've clicked "submit reply/thread" then if you keep the blank/error page open for a few mins and then press F5. It may ask you if you want to submit the information again, which will attempt to make another post.