Problem on plugins page with latest update

Step by step approach to finding Javascript Conflicts

1. Switch temporarily to a WordPress default theme (Twenty Eleven etc.) and see if the problem goes away.

If it does, you’ve most likely got a JavaScript conflict with your current WordPress theme.

If switching to default theme doesn’t help it could be one of the plugins you are using that is causing the problem.

2. Disable all plugins other than Contact Form 7

If doing that solves the problem, you can then add back each item – one by one, until you find the real cause of the problem.

I have tried changing the theme, but this doesn’t resolve it.
I can’t disable all the plugins other than Contact Form 7 because I can’t see most of them! Deactivating those I can see (which is up to Contact Form 7) doesn’t resolve the problem.

It is always possible the plugins didn’t update correctly on your site. It’s a general problem with WordPress updates due to the unreliability of internet connections.

??If you took a backup BEFORE you updated the plugins (we ALWAYS do), you could revert to that and then try to update the plugins again.

If the backup you did for the test site was done AFTER you updated the plugins, I’d suggest you delete all of the plugins you updated by deleting each plugin folder at wp-content/plugins/plugin-name/ and then install each plugin again.

Do this on the test site. Delete all updated plugins, install CF7 first, then add the other plugins 1 by 1, to see if you get the same problem.

Sorry, buzztone. Thanks for the advice, but have not had time to come back to this before now.
I did have a backup before the plugins were updated. Unfortunately I didn’t realise the problem until later as I had updated the plugins from the updates screen rather than the plugins screen.
Today I reinstalled the backup on a test site. I then deactivated all the plugins apart from Contact Form 7 as you advised, which I updated. I reactivated them one by one, updating them as I cam to them. The problem arose again when I reactivated the DropShadowBox plugin. I tried deleting this manually via FTP from the plugins folder but the plugins page was still broken. I deleted the site and started again.
This time I deactivated only the Contact Form 7 plugin (which I had not updated). At this point although the scroller was still visible on the right of the screen it wasn’t showing any plugins below Contact Form 7. When I deleted Contact Form 7 the scroller disappeared and all plugins below where Contact Form 7 should have been on the list were not visible. The page still showed that there should have been a total of 26 plugins but only about 10 were showing. The screen options at the top of the screen were also not working (as was the case initially. I again deleted the site and reinstalled the backup.
Now I deactivated all the plugins and reactivated them one by one from the top, missing out Contact Form 7 and Contact Form 7 – Campaign Monitor addon. I activated and updated Contact Form 7 and all was still OK. However, on reactivating the Contact Form 7 – Campaign Monitor addon the problem arose once more – no scroller and no plugins below Contact Form 7 in the list. I therefore assume this is the culprit.

Now I worked out where the problem is I see on the Contact Form 7 Campaign Monitor add-on plugin forum that this is a problem because the plugin hasn’t been updated to be compatible with the latest version of Contact Form 7.
Thanks for your help on this.
I am installing Gravity Forms to use on the site, which has a functioning Campaign Monitor plugin.