Photoshop Beta suddenly refuses to 'access' full 256 colour range when exporting to gif

[Lauren31083174e65l]

Hi all, 

Recently, my Photoshop Beta has defaulted to only using 35 colours with a gif export (save for web) no matter how many times I select 256 colours and the Perceptual option.

Below you can see my settings and the massive colour shift from blue to green.

Also, the colours that are in the Color Table are all marked with a dot (what does the dot mean?) whereas previously 256 colours would have been used and only some had the dot on the swatch. Please help...

[davescm]

To extend the range of colours turn down/off the 'Web Snap' value - which you have currently set to 100%. The diamonds in the colour table indicate 'web safe' colours.

Dave