phantom block and block placement issue??

[advocatee_]

okay so for starters im new to the whole mod thing so excuse me if i sound stupid. i was playing maybe a day or two ago on a server two other friends had invited me to and i consulted my friends before coming here and everything we didn't work. there's just a phantom block in the middle of my house which other then being semi inconvenient isn't really a major issue. second thing is while working on said house there are two blocks that wont allow me to place anything. when i attempt the blocks leave me hotbar and don't show up where i indented on them being and then they will soon reappear in my hotbar. at this point i dont know if its my computer or what and everyone ive talked to is at a loss:(