Applicatin is closing automatically without throwing any exception.

Hi all,

I have devloped an application in VBA (Excel 2003) which imports lot of data (around 2,00,000 to 5,00,000 rows) from .csv files (as raw files) to .xls files.
These .xls file will be created month wise (date is avalilable in csv files). Tool also creates one log file in which tool writes the number of rows updated from each file with file name and also logs errors if any occured. At a time tool can import 32 files. Most of the raw files are more than 15 MB. Tool takes around 1/2 an hour to import each file. I am using error handeler in each and every function and subroutines, but some times tool gets close without throwing any exception.
The problem I am facing is some times tool suddenly gets closed while running which throwing any exception. From log file we can see that while importing which file tool got closed. And when we try to import the same file second time it gets imported without any error or without closing the tool.
One of our user using this tool in Excel 2010 and he is facing the issue "Automation error: The object invoked has disconnected from its clients". This error is repeating for him in every 2 to 3 days . Problem is also same here when he import the same file second time, tool imports it without any error. I am not able to understand problem and not even able to duplicate the error. Please suggest me something to resolve this issue.

Thanks in advance....