Bicycle Mechanics - Campy gear problem?

I don't know whether to post this here or in the forum on mechanics but I am experiencing 2 problems.
I am posting this in both places, sorry about that.

First, after about a year with my Bianchi Eros with Veloce/Mirage mix I found myself locked in the hig gear a number if times. First happened after about 50 miles in the rain.
After maintenance it happened only once in a while.

I upgraded so the bike now has Centaur derailers and shifters with Veloce and new cables. I took it out for the first time after the upgrade and found 2 problems. I am taking it back to my lbs so they can correct them.

The one problem I now have is no matter which of the three ring up front I am in, when I am in the smallest rear ring it locks up. I can not change the rear derailer. When I tried down shifting I did notice once that the cable appeared loose not taught going down to where it goes under the cranks.
The new problem is when I am in the largest ring in the rear it doesn't seem like it is sitting right, I mean its like its skipping sometimes while pedaling.

Its like having a 21 speed bike instead of 27 because I am okay if I stay off of those rings.

Anyone have similar experience before or have an idea what might be going on?

Thanks

You DON'T have a bike with 27 usable gears. Nobody does. When you are in the big ring, the biggest couple of rear cogs won't work right; when you are in the small ring, the smallest couple of cogs won't work right; and when you are in the middle ring, the smallest and largest cog may not work right. The chain isn't meant to flex very much in a lateral direction, so it can get stuck. This is exacerbated by newer (compact) frames with shorter chainstays. It also sounds like there is a problem with the cable run. Either the cable holder under your BB is messed up, or your LBS changed cables but not housing, and there was always a problem with your housing that wasn't caught before now. Frankly, I think upgrading an Eros to Centaur was not the best use of your funds. I have a 9 year old Mirage grouppo that has always shifted well and behaved itself. Another thing to check is your chainline. When you are in the middle ring up front and the center cog in the rear, the chain should be running in a completely straight line, even through the jockey wheels of the rear derailleur. You might also want to make sure that the front derailleur is parallel to the chainrings and that the cage is set about 2mm above the big ring when the chain is up there. Also, there should be about 1mm between the chain and the inside of the outer plate of the front der when in the big ring, and the same between the chain and the inside of the inner plate when on the small ring. Without seeing your bike in person, its hard to troubleshoot exactly what is wrong, but these ideas should help you get it sorted out. Good luck.