This error generally occurs in the following situations :
Situation 1 - VBA not installed
In case, if you are using Excel 2007 and get the Ole Error 800A03EC while importing data into Tally using udi-Magic, then it is likely that VBA is NOT installed in your system. Upto Excel 2007 you didn't had to install the Visual Basic Editor if you wanted to develop or run macros (VBA procedures). In Excel 2007 you must specify that VBA be installed when you install Excel from the Office CD. See how to install Visual Basic for Application for Excel 2007
Situation 2 - Older version of udi-Magic
If you are using a new template (of v7.0) with udi-Magic v5.0, then you may get this error.
Situation 3 - XML formula error
The aforesaid error may appear in case if there is a Formula error in the XML tags / mapping.