Vista - Vista Home Premium IE7 Show Picture reluctance

I am using a conventional Dual Core PC with Windows Vista Home Premium. IE7
has recently started leaving gaps in webpages that have several images so
that I frequently need to scroll down the page selecting each missing
picture (with its little red x) using "Show Picture" in the context menu. I
am not sure if this is the result of something my ISP has changed (it was
recently taken over by Pipex and then Tiscali), or a Windows update, or my
security software (NOD32 then ESET Smart Security). I think my IE7 settings
are all back at their defaults. An example of a page (one I have created
many months ago with a collection of 136 700x200 pixel Cornish banner JPGs)
that demonstrates the problem well is:
http://www.friendsofthefoweyestuary....in_banners.php
Typically I find groups of two or three successive pictures missing and then
perhaps the next ten or twenty showing normally.
OK - I can live with it, but it rather spoils what I intended to be a
pleasing browsing experience.
(Firefox normally renders the all the pictures in one pass, but sometimes
seems slow to pick up the style sheet formatting, leaving that till after it
has all the pictures.)
I did not have the problem when I first installed Vista. I have tried
various suggestions that I have found via google with no success.
Doug