Thanks for the tip. I tried it but it makes no difference. Oddly, with the very latest version of the viewer and newly updated drivers for the graphics card (this morning) the situation is different and worse. Whilst the sky is back with detail, the sea is a flat, deep magenta colour, as are some other blue things. Also terrible lag and de-rezzing. I think the truth is that cards like ours (and they are no more than 18 months old) won't be able to display the newer SL viewers. I've now gone for a Singularity v1 viewer, as all the 3rd party version 3 viewers I've tried give us serious problems. I think the moral is, don't buy ATI cards if you want to use SL reliably. Difficult though, as many machines come with them as standard (the university only buys from HP and they only use ATI cards now). If there are any Lindens reading this, it's a show-stoppping problem for us.