OPC with Micro 850

Hi everyone.
I'm in a uncommon situation. We designed a filling system with 3 Micro 850 a panel view C600 and one panel view 800.
To start, we had problems with the communication but we could handled it by upgrading the firmware of the Micro to v7.011.
So now i'm trying to implement a database with excel using OPC/DDE from RSLinx.
I can only make it work when the micro has the v4.01x of it's firmware but for some reasons that version makes communication problems in my system, and we don't have the time to check in detail the problem.

i've already tried with all the firmwares available and also changing the revision of the project, but the OPC only works for me in the V4.01x, otherwise it says invalid data.

Does somebody have a clue or an advise??
Excuse my rusty english.

There're several technotes about the topic:

TN520415 - OPC Data Access with Micro800 PLCs Firmware 4.xx or older (Access Level: Everyone)

TN607457 - OPC Data Access with Micro800 PLCs Firmware 7.xx or newer (Access Level: Everyone)

TN567375 - Data manipulation to get string data into Micro850 from Logix or OPC (Access Level: Everyone)