It may have been a bad move as squash roots often like to spread sideways. However, if given adequate fertilizer and water, it may not have mattered. Squash are heavy feeders; a daily feeding of urea and fish emulsion would not be too much. It may be that the variety doesn't like your climate. Has this pumpkin variety grown well for you in the past? Many squash (including pumpkins) are very daylight sensitive. For example, if it was bred to grow well in the South (or even if the seed was grown in the South for a Northern seed company), it may stop growing altogether in the North during the longer summer days, and start growing again when the days get shorter.

If you have never had luck with this variety, try other ones until you find one that grows well for you.

Thanks. I will try again - this time straight into the ground with fertilizers (blush). Oh, and some research.