Unable to connect to at least one database - Randomly

[Skykit]

Hi all,

I have a really frustrating issue with 10.2.1 currently whereby schedules that run throughout the day randomly come up with a fail - Unable to connect to at least one database during a multi-database attach....

This is obviously self-explanatory but in reality it is not at all.
If a schedule runs and fails with the above message, you can immediately run it and it will be fine.
Others that are running at the same time (or started before/after) with the same datasource will work fine.

This is also not just schedule related but even through running reports where you will instantly get a login failed.  Clicking details brings up the same error as above.  Entire error is as follows

QE-DEF-0285 The logon failed.QE-DEF-0325 The logon failed for the following reason:RQP-DEF-0068 Unable to connect to at least one database during a multi-database attach to 2 database(s) in:      SQL1_     Tops UDA-SQL-0031 Unable to access the "SQL1_" database. Check that the connection parameters to the database are configured correctly. For example, ensure that the data source connection contains the signon information, such as a password, to connect to the database.UDA-SQL-0107 A general exception has occurred during the operation "{0}".CCL-COM-0002 Failed to initialize COM because the concurrency model changed.UDA-SQL-0201 There was an error initializing "COM".

Checked:

1. Uptime of database server - Running fine
2. Any brief downtime of network, database server - None
3. Other systems do not suffer that have databases on the same server
4. Left pinging the database server from the cognos server on a continuous ping but no outage.

So where is the issue??

Appreciate any help on this

It's on FP2 currently but 3 and 4 have no changes that I can see which would fix this issue so I assume it is potentially environmental.
Just to add: connection is to SQL 2008 server (Microsoft SQL Server 2008 (SP3) - 10.0.5512.0 (X64)   Aug 22 2012 19:25:47   Copyright (c) 1988-2008 Microsoft Corporation  Standard Edition (64-bit) on Windows NT 6.0 <X64> (Build 6002: Service Pack 2) )

Connection this is happening on is:
Native and OLEDB
Thanks again