I am thinking about buying CS5 to keep up to date.
I cannot do without Version Cue which is only CS4.
Can I buy the upgrade and run them to take advantage of both ?
Yes, you can run both CS4 and CS5 simultaneously, however, you must first launch CS5, then launch CS4. I don't know much about Version Cue or whether it would still work in a CS4/5 workflow, but you could always try the 30-day CS5 Trial as a test.
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