Looks like sun scorch to me Rips.I've got 2 of them and during the hottest part of summer mine get a bit frazzled,but they always pull through.Just make sure the compost never dries out as they like it constantly moist (not wet though).

Be careful though-vine weevils seem to love acers.I almost lost my biggest one about 6 years ago and took several doses of a chemical solution to kill them off.If you dont know what they are Google it and you'll be suprised!

Ooooooooh, that looks like a snakebark to me??? I had one about that size in a pot, but since plating it in COMPLETE SHADE down by my little shed, it's gone absolutely nuts now and is getting like a tree and that was only last year that I planted it outside. I'll take a piccy of mine tomorrow just to compare, but I'm sure the leaves look like my snakebark acer which means when yours grows big, it has this lovely snakebark stem!

Definitely sun scorch going on there, so you've done it a favour by bringing it indoors but if you get the ericacious soil (sp?) and put it somewhere where it will only get the very early morning sun (they do like some sunshine!) it should flourish. Failing that put it somewhere like I have mine, where it will hardly get any is my bet.

One of mine just adores the sun, the leaves never get scorched and it has full sun from mid-day and baking hot up there on the patio, but I'm loathe to move it, and anyway, the pot is too big and heavy to move even if I wanted to!

Ok I've thought about and I'm going to call him Dave!

Urgh, they're horrid! I did find a huge grub when I was digging over the garden, I really hope it isn't one of those!

Ah well at least it's out of the sun. I've put it in a pot and it's outside by the house now in the shade, or should I keep it inside for now? I'll go and get some of that soil tomorrow too.

Mine is an Acer palmatum 'Atropurpureum', although the snake barks look fab! Definitely on my wish list!

Thanks for all of the advice everyone, hopefully Dave will flourish now I know how he should be treated!

Hope Dave lives a long and happy life.

Thanks so do I, he's still looking a bit sickly at the mo but fingers crossed!