Mem, thank you very much for the feedback.
The relatively high ratio of failed checksums is a little worrisome. I usually only get 1 or 2 in an hour-long run with my EM406A. I hope it does not indicate a latent bug in TinyGPS checksum calculations, although I note that some of the sentences passed or you wouldn't have gotten any good data. Are you using the revised AFSoftSerial library?
Thanks!
Mikal