Coordinate subscripting problems

I am encountering some very strange behavior using variable
subscripting on some NCEP-II data. If anyone can give me some insight
into what's going on, I'd appreciate it.

I've attached a script that demonstrates the problem I'm talking and
the output from that script, but here's a short summary:

I'm running NCL 4.2.0.a033 on a linux machine. I have NetCDF file with
data from the NCEP-II reanalysis (air temperature, in my example, but
it happens with other files as well).

I'm reading in data with a line like the following:

     temp = short2flt(fin->air(time|:, level|0, {lat|LAT}, {lon|LON}))

I'm selecting a single point, so NCL selects the closest value. If I
slowly change LAT from a value near one point in the latitude
coordinate variable array (a grid center) to another, the data values
change when it's halfway between, just as I'd expect.

Here's the weird thing: the data values *also* change when I'm changing
from one side of a grid center to the other, and, moreover, I get a
third value if my latitude is exactly equal to the grid center
latitude. This doesn't happen with longitude.

Any ideas what's going on?

Thanks,

--Seth McGinnis

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