When you copy a sheet from one workbook to another, any named ranges
which are used by the sheet go with it (still referenced back to the
original workbook). So, in creating your second workbook (you don't
describe how), you may well be taking some of the named ranges from
Book1. If you then copy and paste this into Book 3, your ranges will
also be transfered with it.

I don't know why one particular range should cause the slowdown, but it
might be worth examining how you create Book 2 and think of
alternatives to copy/paste.

Hope this helps.

Pete (from Woolston!)