HI Harry,
Select the Infocube->Manage-->Under Performance tab--> Click on Delete DB Indexes (Now) and then
Click on Check DB Indexes tab (Whether its delete i.e RED Status)
Try to Load DTP now.
If its loaded successfully, dont forget to Click on Repair DB Index (Now) under performance and Click on Check DB Indexes tab (Whether its Created i.e Green Status)
Thanks
Anish