Crystal Reports Formula causing exception at runtime

Message

     Hi,

I seem to have a problem with a particular report which has been ported from Crystal 8.5 to Crystal 10. I am using Visual Studio 2008 to preview the report and it all works correctly, shows the correct data no problems.

When I try to load the same report with the same parameters within the cyrstal report viewer in ASP.Net I get an exception in one of the formula fields. The formula is below:

stringVar sAddress := "";

If NOT IsNull ({usp_CMLSIMClaimReport;1.Address 1}) THEN
    sAddress := Trim ({usp_CMLSIMClaimReport;1.Address 1}) + ", ";
If NOT IsNull ({usp_CMLSIMClaimReport;1.Address 2}) THEN
    sAddress := sAddress + Trim ({usp_CMLSIMClaimReport;1.Address 2}) + ", ";
If NOT IsNull ({usp_CMLSIMClaimReport;1.Address 3}) THEN
    sAddress := sAddress + Trim ({usp_CMLSIMClaimReport;1.Address 3}) + "  ";

sAddress

The exception is "a string is required here". My question is, why is this report working fine from with in VS when I select preview however it is causing a run time error through ASP.Net. Any help would be greatly appericated. 

Cheers,
Ash