I looked at your link but it seems to be addressing Win98 & OE5, I`m on XP SP2 &OE6 (I should have said).
Having said that, all that apply are good and as I say it doesn`t happen every time - only occassionally. I feel (right or wrong) that it has something to do with the boot order but I have no idea what or how to find out.
As for Thunderbird, I did try it when I installed Firefox but we didn`t get on!!
Thanks for the suggestions. Anyone could hit the nail.