Is my .shp file corrupted? Problem with symbology.

I have a .shp of polygons representing different land uses.

It was working fine yesterday. However when I opened it today it's not functioning as it should.

I have 30 different land classes. I've symbolized them according to the relevant field.

However the symbology no longer works. The polygons all display in one colour and this colour changes whenever i move around the screen or zoom in.

Now when I click on the identify button on the polygons it returns the value according to what colour all the polygons are displaying. So if all blue the id shows inland water. If the colour for coniferous trees. The id shows coniferous trees.

Can I do anything to save this file or it is corrupted?

Thanks for any help