Queries Going To Suspend State With Wait Type ASYNC_NETWORK_IO

Recently we observed a problem. We are running stored procedure through our c# code. Three machines access the server and update or insert in the required tables in the server. If there is no data in the server, on installing first time our application usually our database is clean. then stored procedure works fine, it takes around 10 to 15 sec to execute. Next time if execute the time goes up to minutes like 15 mins. Next time it goes for hours around 4 hrs. Even to update 4 or 5 records it takes time. Initially we thought it was because of the size of the data and we tried to re tune on indexes, it did not solve. But now what we observe is even with less number of records in server also it wouldn't come of the execution for hours.
Now are executing the just the SP in the SQL manager studio to see the time. That one also is executing for hours. when looked at the activity monitor the process goes to suspend state with wait type ASYNC_NETWORK_IO.

When we comment one of the query is working fine.
Is this something to do with the query I am not sure. If that is the case it should not work every time.

The query makes any sence or is there any way to write it in better way



'UPDATE [server].[dbo].[DocumentMetadata] SET DocumentInfoID = b.DocumentInfoID, [Name] = b.[Name], MetadataType = b.MetadataType,
[Value] = b.[Value], ValueType = b.ValueType
FROM [server].[dbo].[DocumentMetadata] a WITH (UPDLOCK)
INNER JOIN (SELECT c.DocumentInfoID, c.[Name], c.MetadataType, c.[Value], c.ValueType
FROM MACHINENAME.[Client].[dbo].[DocumentMetadata] c
INNER JOIN MACHINENAME.[Client].dbo.DocumentInfo DINF ON c.DocumentInfoID = DINF.DocumentInfoID
INNER JOIN MACHINENAME.[Client].dbo.Path d on DINF.NativeFileID = d.PathID
INNER JOIN MACHINENAME.[Client].dbo.ActiveDataSource ADS ON d.DataSourceID = ADS.DataSourceID
WHERE ADS.ProjectID = ''' + @ProjID + ''') b
ON a.DocumentInfoID = b.DocumentInfoID AND a.[Name] = b.[Name]'




'INSERT INTO [server].[dbo].[DocumentMetadata]
(DocumentInfoID, [Name], MetadataType, [Value], ValueType)
SELECT c.DocumentInfoID, c.[Name], c.MetadataType, c.[Value], c.ValueType
FROM MACHINENAME.[Client].[dbo].[DocumentMetadata] c
INNER JOIN MACHINENAME.[Client].dbo.DocumentInfo DINF ON c.DocumentInfoID = DINF.DocumentInfoID
INNER JOIN MACHINENAME.[Client].dbo.Path d on DINF.NativeFileID = d.PathID
INNER JOIN MYCLI.[Client].dbo.ActiveDataSource ADS ON d.DataSourceID = ADS.DataSourceID
WHERE ADS.ProjectID = ''' + @ProjID + '''
AND Ltrim(rtrim(c.DocumentInfoID))+ ltrim(rtrim(c.[Name])) NOT IN
(SELECT Ltrim(rtrim(DocumentInfoID))+ ltrim(rtrim([Name])) FROM [server].[dbo].[DocumentMetadata])'



We have been fighting it out for so many days.
Can anybody help

Thanks
knvdssr