If you reload that should clarify the situation. Also I believe their is a keystroke that does the same thing, but I don't remember what it is
I've been thru this so many times with other people. They are ghost blocks that never go away. Cant place anything there at all. It's been like that for a week
Ghost blocks are typically blocks that will re-appear after a relog (e.g. after using super breaker, a lot of people experience blocks that they can't walk through.) However, there are occasionally areas that have ghost block 'bosses' as one might call them. Dropping sand or gravel into them, or using a piston to push a block into it, will sometimes remove them. However on occasion, this won't work either and it required Jordan to spawn in bedrock over it and then remove it again. Sounds like you're in need of Jordan's assistance this time around. I'll post the co-ords for him to fix when he gets the chance. Could you post whether this is in the new world or old world? Thanks! For future reference, you can contact a staff member in game or post on the forums and we'll get it fixed ASAP.
I've sent Jordan the co-ords and world. He's the only one who can get rid of them, so when he next has the chance he'll do it. Sorry for the inconvenience!
You can get rid of ghost blocks by placing sand a few blocks above them and leaving it to fall on top of it.