We've failed to reproduce the problem with the Borland StringGrid sample included in TestComplete samples: the ClickCell method scrolls the grid to locate the specified rows and columns if they are invisible and does not post any errors to the log. Please reproduce the problem, zip your entire project suite folder along with the log of the failed test execution, and send us the archive. Make sure that messages in your log correspond to the latest version of your tests.
Set objString = Sys.Process....StringGrid
colCnt = objString.wColumnCount
rCnt = objString.wRowCount
For i = 0 to rCnt - 1
If objString.wValue(i, 2) = "Cell Value" Then
Call objString.ClickCell(i, 2)
Log.Message("The Item 'Cell Value' was selected")