Theros card Dark Betrayal does not appear to be addable to the sideboard of a decklist. I repeatedly receive error message "Cannot find card. Please choose one from the autocompleted dropdown" while using the "quick add" feature, whether I select the card from the dropdown or not.

Edit: having the same problem with Magma Jet.

Could you tell us which browser are you using?

Make sure there are no extra/hidden characters or spaces. I have had this problem before as well and it is usually because of an extra space somewhere

There were definitely no extra spaces.

Browser is IE8 (I know, I know! It's atrocious, haha. But it's my work computer and IE is the only browser they let us use on it.)

Tried both cards again just now via the same method, still same result as before.

Are you typing it by hand or copy/paste?

Typing by hand, did not try to copy/paste but I can give it a whirl if you think it'd work better.

Multiple attempts to add the card by typing the card name in full and hitting enter, as well as multiple attempts typing a partial card name and the clicking the relevant cardname from the dropdown list that pops up. Both methods have the same result.

Definitely an IE8 issue then. We will look at this today I hope, we have another 2-3 other reported IE bugs to look at.

Not sure why but I tried in IE8 and this does not happen to me. Can anyone else also check this please? El_Panda, this is still happening for you?

Yep it's still happening, just tried again for both cards and same result as before. It actually happened again the other day with a different deck and a couple of different sideboard cards, but I forgot to write down which ones they were.