Thank you all !
I've just applied the 7.0.1456 Avast version on the both hosts concerned by the problem.
Honestly, since I was very confident in Avast, I did not think about taking a look on Avast forum ! Warm thank to BobCat13 for the link which describes perfectly the situation of the last 3 days.
As I wrote my assumption regarding a memory leak, it was the result of a pure theoretical analysis since it was not possible to perform any "post mortem" investigation and because the information provided by the Windows task manager did not really show the problem.
I did suspected initially the recently applied Windows updates since I observed some inconsistencies after the update; e.g. the reported boot time is incorrect since the last update.
I assumed that a memory leak would be quiet improbable, especially by avast. Software should be tested and a memory leak is one of the most important test during alpha and beta test phases.
Anyway, the made experience shows that software development organizations should use boinc applications for load testing and load simulation. Many deep inconsistencies in the software become visible by running crunching projects.
Hopefully, the provided patch was the right one ! ...
Cheers,
Yves

Great, then please OP Title edit in [RESOLVED]

(my W7-64 never skipped a beat with .1451)

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