Resolutions in lonlat

I have some high resolution data in a UTM location I want to
convert to a lonlat location. I figured out a lon-lat resolution
that should accomodate the data, but when I try to use
i.rectify's option to set region to minimal area, it rejects
my propsed resolution as "Illegal resolution". I messed around
to see what it would accept, and tenths of a degree seem OK,
hundredths are OK, but it seems to reject thousandths of a degree.

Am I missing something? How do I get a high res raster into lonlats?

Neel Smith
nsmith@abacus.bates.edu