I have the same problem with installation of package for Cat3750.
I have seen in the readme files for Cat3560 and Cat3750 that both need to have installed the DtShare V1.10 (DtShare.cv50.v1-10.zip) first.
On my CiscoWorks there is actually installed DtShare V1.9, but it seems that there is no DtShare V1.10 ready to download via Common Services - Software Center - Device Update. Also the manually download of the packages via CLI gives me only the DtShare V1.9.
So I assume that we have to wait until Cisco makes the DtShare V1.10 available.