Having trouble with my Pro-ject 9

I just bought a used Pro-ject 9 here on Audiogon and I'm having trouble with skating. I can't lower or raise the tone arm without it moving in either direction. I have tried altering the weight on the back and leveling the table, nothing has helped so far.
I had no problem adjusting the height but I did notice that only one of the two allan screws in the back of the tone arm works. The other one screws in snug but won't hold the arm up. Any suggestions?
Apologies if this seems too obvious - did the seller include the little weight on the fishing line? Not sure if you were referring to adjusting that or the big counterweight on the end of the arm. I've had two tables with the pro-ject arms and they are unusable without the fishing line weight. Only other guess is the arm is not mounted quite right, perhaps the horizontal bearings may not be level even though the table is . . .

Thanks Zargoz for the reply. The arm seemed to work better with the line off it. I re-balanced the tone arm and it worked better. Now I need to find a cartridge that will warm up the sound.
One thing I found w/ my 9.1 was that sometimes the bottom of the tone arm where it meets the arm rest gets 'greasy' and makes the arm a lot more susceptible to it moving around when raising it. Not sure if that was what you were stating or not.