laptop - Some keys when pressed insert two characters

I have a Dell Inspiron 1545 runnning Windows Vista.

For a while, the keys "t", "y", "[", "]", "5", "6", F7, F8, F9, and backspace refused to respond most of time. I reconnected the keyboard wires, and they now respond. However, when I press one of those keys, it inserts two keys at once. For example, "t5", "y6" backspace and F9, F8 and F7.

Any idea how to fix this? Also, there are moments where this seems to repair itself, but returns eventually.