If you've loaded August CU for Project Server 2010 – KB 2276341, but haven't loaded either SharePoint Foundation 2010 August CU (KB 2266423), or any of the rollup packages (KB: 2352346, 2352342 or 2352345) then you'll get an error loading the schedule web part and drilling down into a project - or other pages that us the JSGrid.
The error will be this one:
To resolve: load one of the Aug CUs that contains sts-x-none.msp, which would be any of following (see KB articles linked above in order):
Description of SharePoint Foundation 2010 hotfix package (Sts-x-none.msp): August 31, 2010
Description of SharePoint Foundation 2010 CU Server Hotfix Package (SharePoint Foundation server-package): August 31, 2010
Description of SharePoint Server 2010 CU Server Hotfix Package (MOSS server-package): August 31, 2010 (Doesn't include Project Server patch)
Description of SharePoint Server 2010 and Project Server 2010 CU Server Hotfix Package (MOSS server-package, Project server-package): August 31, 2010
"Although JSGrid is a component initially developed for Project Server 2010 it was shared with other teams for "14" release and is also used by Access Services. It's shipped as part of SPF, and this's where we slipped up in not having fix in the PS CU too," stated Microsoft.