cvs version of ecommerce with cvs or 4-7 version of drupal ???

ecommerce cvs/4.7 is not stable yet.
Not sure about your problem though, you haven't supplied much information.

I would recommend ecommerce 4.6, unless there is a specific feature of Drupal 4.7/cvs that you want. ecommerce 4.7 would be possible (IMO) but only if you are willing to get your hands dirty, and certainly there are many contribs which have not been updated (ie. to the new forms api).
HTH, Simon

this is very true. unless your looking to see what features are going to be available to you after the update or are really interested in getting you hands dirty watching cvs logs and/or playing with code, the cvs isn't the place you want to be.

You can use ecommerce cvs with drupal cvs or drupal 4.7 Beta.
But, like sime says ecommerce cvs is a work in progress.