My terrain setting is normal, and visibility is to 900 but as Bugsfrombis said, that should be irrelevant, as I had not change any settings from when I was running 1.85. The only time I had to mess with the settings was when Resistance came out and the performance drop was not so big then as it seems now. I have always used the same mission in the editor to test performance. It seems BS is expecting us to continually update our computers to play the latest patch!
On another note I was getting the "cannot memory map 1985.pbo" message and CTD before updating (which prevented me playing the campaigns) I tried all the fixes for that suggested on theavonlady`s site, to no avail. After updating to 1.90 I got a config bin error relating to an addon and still got the memory map error. I deleted the addon and strangely enough all started working again?? The addon was called squarecanopy.pbo.