Strange problem when updating database

Question

I have an odd problem with a small application that is written in VB.NET, reading from and updating an SQL Express 2012 server.  The app pulls a datareader from a view and then loops through it and sends each record to an offsite db via an http post. 
It then goes and marks the record sent using an update query to set a sync bit value in the main key table.  It then goes to the next record in the reader and repeats the process (or that was the idea). 
What happens when it runs is that the update operation fails with a “Connection timeout or server instance not found “ error.  I have checked the usual culprits, it connects to the server to retrieve the reader OK using the same connect string, the
user in the connect string has appropriate permissions to the table in question, etc.  The event log only shows an unhandled exception, the timeout message appears in the local debugger.  The exact same update runs successfully on another table for
a different operation and on my dev machine, so it seems to be something about that particular table. 
If I log in to SQL management studio as the user that I have in the connection string and update a record in the table using the same syntax as the update query in the application it succeeds.  Very strange.
Troubleshooting is somewhat complicated by a need to be very careful with the machine that the problem is occurring on.  It is an in-production machine that I can only access via Logmein and is a 20 hour plane flight away.  So I have to be very
cautious not to bork it up.  Any thoughts on how to proceed?

Answer 1

I have an odd problem with a small application that is written in VB.NET, reading from and updating an SQL Express 2012 server.  The app pulls a datareader from a view and then loops through it and sends each record to an offsite db via an http post. 
It then goes and marks the record sent using an update query to set a sync bit value in the main key table.  It then goes to the next record in the reader and repeats the process (or that was the idea). 
What happens when it runs is that the update operation fails with a “Connection timeout or server instance not found “ error.  I have checked the usual culprits, it connects to the server to retrieve the reader OK using the same connect string, the user
in the connect string has appropriate permissions to the table in question, etc.  The event log only shows an unhandled exception, the timeout message appears in the local debugger.  The exact same update runs successfully on another table for a
different operation and on my dev machine, so it seems to be something about that particular table. 
If I log in to SQL management studio as the user that I have in the connection string and update a record in the table using the same syntax as the update query in the application it succeeds.  Very strange.
Troubleshooting is somewhat complicated by a need to be very careful with the machine that the problem is occurring on.  It is an in-production machine that I can only access via Logmein and is a 20 hour plane flight away.  So I have to be very cautious
not to bork it up.  Any thoughts on how to proceed?