Say I have several IPs, the only mention in the rules as to when you can't interrupt is that you can't take more than the first action from the next combat round during this combat round. Does this mean that (using the MA rules from arsenal) I can use both riposte and finishing strike in response to someone making a melee attack against me? (this would be 2 interrupts in a row, thus pulling my next 2 actions. so as long as I haven't already used my last IP for something I think this works.)

In a similar vein, could I use the finishing move maneuver multiple times in a row? (until I have used the first action from the next combat round, and thus can no longer use interrupts.)

Finishing Move requires that you hit and do damage- i.e. you are the attacker.
Reposte requires that you successfully parry or block- i.e. you are the defender.

As you cannot be both, you cannot stack these abilities.

One might argue that as a defender you could use Reposte first, hit your opponent and then use Finishing Move, but I would not allow this at my table.

On second thought, it would be a very specialized character that had both abilities, and I could see it working fluff-wise. I might allow it if the player really sold me on the idea, but I would charge them 2 subsequent APs. And it couldn't happen on the character's last AP as the BBB specifically says you can only bump the first AP of the next turn (SR4A page 148).

[edit for clarity, etc...]