I believe this may be the answer. I have
seen the identical issue on two separate
12.3 routers of the 1751V type.
Same errors exactly.
Different local PCs running at the time, so I don't think it's related to anything internal. Different memory in the actual router, and I even increased the actual physical memory size to no avail.
BTW, I put back online an old 821 router,
and it did the same thing.
I believe this mainly started happening when I put P2P applications on a Linux server.