Elkin,
Log onto Data Manager, navigate to tool bar and Click on Help --> Repository Info --> Role.
Suggest you to cross-check if you have Admin role assigned to your credentials. If Admin role is assigned then you should be able to export.
From the above screenshot i could see that role : Admin has active functions to export records in data manager (Hopefully screenshot is from Data Manager tree ).
As a work around, if you are in real hurry to export data, then u can export selected records through syndicator in a text format. Until we find a solution you can use this as n alternate option.
Regards,
Kasim