RW7 Preview Error

I keep getting this error when trying to preview my blog page within RapidWeaver 7.0.2. I’ve talked to Lucas and Archetyphon (using his Polygrid theme for my blog) and he says it’s a RapidWeaver problem. I’ve had this problem since RW6 and still no fix. Any ideas…? Thanks, Billy.

Exception while exporting site
Error: Could not copy /Users/billymiller/Library/Containers/com.realmacsoftware.rapidweaver/Data/Library/Application Support/RapidWeaver/Themes/Polygrid.rwtheme/Contents/template/polygrid/index.html to /var/folders/qm/cvcz63ss30z6k2sz8g9qvzz00000gn/T/com.realmacsoftware.rapidweaver/RapidWeaver/585/document-0x7ff86c196850/RWDocumentPagePreview/setup-shots/template/polygrid/index.html.