I am also experiencing this problem on Rev 67 and have also tried Rev 69.1 and the same problem occurs there. Also, applying the SYS_REPO.ACTIVE_OBJECT rollback to 30 Nov fixes access to the file. Here is the revelevant info (it is part of the HTTP response from the xsengine service) from the dev_webdisp file that is causing the failure where you can see Dec is missing and there are 4 nuls in between GMT and the newline:
0d0a6c61 73742d6d 6f646966 6965643a |..last-modified:|
20547565 2c203033 20203230 31332030 | Tue, 03 2013 0|
303a3433 3a303320 474d5400 00000d0a |0:43:03 GMT.....|
436f6e74 656e742d 4c656e67 74683a20 |Content-Length: |
37300d0a 0d0a |70.... |