If the problem is that recent, a System Restore may undo it for you. True, if you fix the problem by restoring to a previous time, you won't know what it was that caused it --- but if it doesn't happen again, then 'no harm - no foul.'
Not all data can be copied. For example, while some text may look like text, it may actually be part of a bigger image.
And some documents, like locked pdf documents cannot have parts of the document copied either.
Well, if you post exactly what it is you are trying to copy, we can see if we can, or cannot copy it too.
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