I can confirm that the SVN 9548 didn't display those warnings only because it uses a printf instead of appending them to the logfile. Everything is EXACTLY as Stu Redman as said. I've replaced the printf in MuleUDPSocket.cpp and rebuilt the SVN 9548 and I've got the same behaviour with the only exception (quite a big one though) that the router and the swapfile remain stable. I've also understood what causes those warnings: as already guessed by freddy77, they arise when the connection drops.
After making these verifications, I've built the latest SVN 9852 as I've done before with the SVN 9847 (I've patched PartFile.cpp to disable the Corruption BlackBox) but this time I've also patched MuleUDPSocket.cpp to disable the visualization (not the handling) of those warnings.
The warnings aren't there anymore (obviously!
) but, even with the Corruption Blackbox disabled, the router isn't stable and the swapfile crashes (unlike what happened with the previously built SVN 9847 that wasn't much stable too but at least didn't make the swap crash).
I've to add a slightly off topic issue: aMuleGUI isn't stable at all and has often crashed while all the previous versions that I've tested (even the SVN 9847) were very stable. Has something related to aMuleGUI changed in the meantime? If yes, maybe that checking those modifications could be necessary.
I would surely have to use a version much older than the latest ones: they definitively have something too hard to handle for a router with limited resources (unless you could give me some other advices like the one on the Corruption BlackBox). It's a pity cause the newer versions are much better than the SVN 9548...
I hope that my testing has been useful and thank you all (especially Stu Redman whose advices have been very useful) for your help.