Crystal report vb.net export problem

Hello,

We are working with VB.net and crystal reports with sql server2000 as
database,the problem is that when we open a report and export it via
default utility in crystal reports it works fine but once we close
that report and open report again it gives error on line where we load
the report??

Gives error as loadsave reportexception: load report failed.
If we reopen the application it works fine only once it doesn't open
again after we export the report to ANY format???

Can anyone help me on this.

thanks
regards
Gurmukh