i have game crash every time i attempt to lvl-up card, does not matter which kind of rarity/which kind of wild card. different browsers. it starts after last maint.

Same case here, can't upgrade cards, n r or sr, and i have gambit slayer to upgrade... damn

Also clear cache and cookies done nothing, server side problem it seems.

That's odd. I pulled the alpha SR slayer a few hours ago and dumped Wild Cards on her to max her out and had no problems.

they fixed it already