T-SQL (SS2K8) :: Arithmetic Overflow Error Converting Varchar To Data Type Numeric Message When Field Is Decimal

I am trying to setup an indicator value for an SSRS report to show green and red values on a report, based on the NRESULT value. The problem I am facing is that I have several different CASE statements that have the same logic, and they are processing just fine. NRESULT is a decimal field, so no conversion should be necessary. I do not know why I am getting the "Arithmetic overflow error converting varchar to data type numeric." error message.

Below is the CASE statement where the error is occurring. It is in the part of the ELSE CASE. The first CASE works just fine when the ELSE CASE is commented out. If I also change the ELSE CASE statement to say "else case when LEFT(NRESULT,1) = '-' then '0'", then it processes fine, too, so it has to be something I am missing something in the check on negative values. I do need the two checks, one for positive and one for negative values, to take place.

case when LEFT(NRESULT,1) <> '-' then --This portion, for checking positive values, of the CASE statement works fine.
CASE WHEN LEFT(ROUND(NRESULT,2),4) between 0.00 and 0.49 THEN '2' --Green
ELSE CASE WHEN LEFT(ROUND(NRESULT,2),4) > 0.49 THEN '0' --Red
ELSE '3' --White
END
END
else case when LEFT(NRESULT,1) = '-' then --This portion, for checking negative values, of the CASE statement is producing the conversion error message.

[code]....

I checked the NRESULT field, and there are not any NULL values in there, either.