chainring skip?

In article <[email hidden]>,

Luigi de Guzman said:

I've just replaced my chain & cassette, and after much fiddling with the
adjuster screws on my rear derailer, can't seem to get it to run skip-free
and quiet.

Most disturbing problem--occasionally, shifting into the second cog (rear)
from the middle ring, the chain will come off the chainring...but only
partially. It neither derails completely (which would put it onto the
granny below) nor engages, it just...half-snags, making a terrible grating
noise.

what's going on here?

One of the links in your chain might be too tight. Or you might change
the cables, too.

--
fneep

Check the shape of the teeth on your chain rings. They might be worn
too. You can take them off and flip them around to use the other side
of the tooth or replace them.

http://www.sheldonbrown.com/chains.html

Luigi de Guzman said:

I've just replaced my chain & cassette, and after much fiddling with the
adjuster screws on my rear derailer, can't seem to get it to run skip-free
and quiet.

Most disturbing problem--occasionally, shifting into the second cog (rear)
from the middle ring, the chain will come off the chainring...but only
partially. It neither derails completely (which would put it onto the
granny below) nor engages, it just...half-snags, making a terrible grating
noise.

what's going on here?

-Luigi