Can't select blocks, pop up showing in black instead of white

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Hi all, when I try to add a new block the pop-up is reversed out showing in black and disappearing after a second or so (attached) leaving me unable to add or edit a block.

I am also having problems selecting some of the blocks on my page when I'm in edit mode.

Hopefully someone has an idea of what the problem is as I'm in a major rush... Thanks for any help.
JP.

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DanK replied on at Permalink Reply
Would anyone have an idea of what the above problem could be? Struggling for time on this one and would really appreciate some help.
Thanks.
JP.
DanK replied on at Permalink Reply
Anyone?