Google geocoding fails but address exists when entered into google maps web page -

i'm doing geocoding our web app google api , getting 602 error when put address google maps search finds location perfectly. seems happen less 5% of time. else come across this?

the url i'm using geocoding this

http://maps.google.com/maps/geo?q=1062+n.+main+st,bowling+green,oh+43402&output=csv&key=xxxxxxxxxxxxxx

if go maps.google.com , put address in, finds perfectly.

1062+n.+main+st,bowling+green,oh+43402

the zip code not part of record in geocoder, if remove it, geocoder can resolve address:

http://www.geocodezip.com/v3_example_geo2.asp?addr1=1062%20n%20main%20st,bowling%20green,oh&geocode=1