I have problems sync two iPad's using one PC?

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I have used the same windows 7 PC to sync my iPad 2 and iPad mini and It worked last time. Now after my iPad 2 is upgraded to os8, when I connect my iPad 2 to PC, iTunes sometimes shows iPad 2 but later changed to iPad mini automatically. Even I ejected iPad mini, iTunes still keeps showing it when actually iPad 2 is connected. Results of sync: photos keep syncing after disconnected and keeps spinning forever. Please help.