I think you have accidently pressed control when clicking one of the tabs -
try right clicking and selecting 'ungroup all'.

btw, this grouping is useful if you want to do stuff like have the same
header on every sheet etc

"seafarer" wrote:

Help - my spreadsheet is frozen on 1 sheet in the file & I can't move to
another sheet - it seems to be 'selecting' the other sheets I try and access
have tried saving as another file but still same error