If it is indeed an SqlException that is thrown (and it does seem like it is from your description), I don't have an explanation. However, you could do the following, and then examine the details of the Exception object.
try
{
Execute a Get stored procedure to read data from a table
}
catch(SqlException sqlEx)
{
log an error
}
catch(Exception ex)
{
// Examine the properties of ex here
// to get a better understanding.
}