"DaveMoore" wrote...
....
During the course of my work I quite often copy a worksheet by CTL +
left click and dragging.
Something has changed whereby now when I try to copy a worksheet by
this method I get a 'no entry' sign (circle with a slash through it).
I've checked all the tabs in ToolsOptions but cannot see anything
relevent.
....

First thing to check is whether the workBOOK has somehow become
protected. Protected workbooks prevent worksheets being moved, copied
or deleted. Either RIGHT click on a worksheet tab and see whether the
Move or Copy... command in the pop-up menu is enabled or not, or run
the menu command Tools Protection and see whether the submenu
contains an Unprotect Workbook command rather than Protect Workbook.