Ticket supplied has expired (Event IDs 1305, 1315)

Good day everybody,
I am seeing repeated event log entries for "Forms authentication failed for the request. Reason: The ticket supplied has expired.".
Event detail code: 50202. Web Event. ID 1315. Source: ASP.NET 2.0.50727.0. Process ID 484. w3wp.exe.

Tried adding the health monitoring tag suggested on Tess' debugging blog to get some more detailed events for this issue so I also see this:

This event tends to be preceded by event 1305, Event code 1003, "Application compilation is starting" (e.g. 8 seconds before event 1315).
Then, 20 seconds later, event 1305, "Application is starting" occurs. Process ID 3788 w3wp.exe.
Then, 1315 pops up again 10-20 minutes later saying "ticket supplied has expired..", as above.
Then, two minutes later, another event, 1305, "Application is shutting down.Reason: Hosting environment is shutting down". (Detail Code 50002).

I read some pos ...