Excel 2010 Non-responsive

[USAOz]

I have a VERY annoying problem with Excel 2010 FREQUENTLY failing to initiate an action - usually involving unhiding a large number or rows or columns.

EVERY time I select a range of rows (or columns) to hide or unhide, Excel stops responding [ top bar says 'File name (Not responding) ].

I thought maybe it may have something to do with the sheet being protected so tried unprotecting the sheet but it still happens.

Any idea of WHY this is happening and how I can stop it from happening? This is seriously impacting upon my work!