My Personal Opinion based on my Personal Experiences:
When I worked at this company I was constantly harassed by another employee. I did everything I could think of to have this employee resolve his/her distain for me.
After about 7 months of dealing with it on my own, I notified HR, who shortly after blamed me for the problem and also didn't believe me. According to HR, I didn't have written proof of harassment. Of course at the time, I didn't know I was being harassed.
A few months went by and there seemed to be no improvements on his/her behaviour.
Later I was provided a task without a deadline. Magically a deadline popped up out of no where. I was let go for not being "efficient." Yet after I was let go they had 3 people working on this task.