Office 2007 on a Windows 7 PC. A user has an intermittent problem where when she copies a cell with a formula in it, clipboard picks it up as text. Typically, if one pastes a copied cell with a formula it also puts the formula in the cell. Not always with this one. Likewise the drag feature where one can grab the lower right corner of a cell and drag it down to past the contents of that cell into the cells below. Doesn't work sometimes. Similarly large numbers (13 digits) copied paste to a cell in text and are jacked up.
We've tried closing Excel and reopening. Rebooting. Even a complete uninstall and reinstall of Office. Not helped.
Any ideas?

Copy the cell, then right-click in the destination cell and select Paste Special. In the dialogue box, check the Values radio. if it does not work, check All. I hope this works.

Agbenaza has a good workaround.

I'd be interested to know, functionally, if you have all service packs and updates loaded. Also, are macros turned on or off on this sheet?