Problems with Colours in documents

Hi,

I'm having a few problems with colours in a few of my documents, it only seems to happen to certain files.

I created some new artwork for a client of our's and they were happy with the final version. I went to open the file a few minutes later (ready to export it to our printers) and certain colours had dissapeared/changed colour. Looking at the document colours, the purple that I had chose (and use all the time) had changed to ID:4 Density 100%?!? I changed them all back to the colours that they were supposed to be, saved it, and closed it to try it again. Exactly the same - all the colours had changed.

Not too sure what's happening or what's causing it, we have a sidebar palette that we use as default for every artwork. Some of our in house artwork containing the same colours opens perfectly.

Any help would be greatly appreciated.

Kind regards,