Files Spontaneously Corrupt

[Piglette]

Sometimes when I return to my computer after an hour or so while it was left running (locked), I find some (but not all) files of multiple types have spontaneously corrupted. Attached is an example of what happened to a text file. Reboot and all is well again. Without rebooting, I have not seen files "recover." The byte count of the bad files is unchanged from that of the original good files.

Make a copy of a "bad" file before rebooting - the copy remains bad, while the original has become good again.

A local copy of a file in a folder on an entirely different path down from C:, made while it was still good, also turns bad as if they were connected by an invisible thread. A copy of a good file made to the network before the problem strikes, looks fine when viewed on the share and when copied down to the local machine, continues to look and function fine while the original continues to be unusable.

Happens on 2 Dell Latitude D630 laptops while connected wirelessly to my work using Cisco Secure. Laptops are freshly imaged with SP3 and pass Dell diagnostics and chkdsk /r with no errors. Full virus scan - clean.

Has anyone ever seen such a thing before?

Thanks

Lukas

[HansV]

It looks like the files don't really get corrupted, but that your system spontaneously switches to a different code page (character set). Something similar, but less dramatic, used to happen to me in Internet Explorer when I had a PC with Windows XP - for example, while I was typing a reply in Woody's Lounge, different characters than the I was typing appeared on the screen. Closing and restarting Internet Explorer usually made the problem go away. I haven't experienced this problem since I got a new PC with Windows 7.

I don't have an explanation or solution for this problem; I hope that a Windows expert will be able to help you.

[Piglette]

Thanks Hans:

The actual file contents change - not just the screen representation. The following shows the first 20 bytes of the original file followed by the ASCII decimal value followed by the ASCII decimal value of the corresponding byte in the bad file:


/ 47 106
* 42 250
13 225
10 52
32 176
32 55
32 181
1 49 77
1 49 200
/ 47 247
0 48 9
1 49 4
/ 47 30
1 49 15
0 48 192
32 33
- 45 87
- 45 166
32 136
B 66 74

[Piglette]

I now know what is happening, and how to workaround it, but not the why.

Our laptops have policies that enforce EFS (Encrypting File System) on many folders and subfolders. This process is supposed to be real-time and transparent to the authorized user. For reasons unknown, this is not the case in our enterprise. The encryption or decryption can lag behind the opening of a file and produce visually startling results/unusable files. (Since my last post, I have found that walking away from the machine for an hour or two will in fact solve the problem - it "catches up").

Encrypted files show their filenames in green text, unencrypted in black.

The workaround is documented elsewhere.

So the remaining question is: what is depressing the operation of EFS?

Thanks

Lukas

[HansV]

No idea, but try TrueCrypt. It's free, and it has been working flawlessly on many PCs where I work for years.

[JoeP]

It appears that something else is using machine resources to the point that the encryption/decryption is being slowed.
If the PCs are locked down by corporate IT they should investigate what is running and how to get around the issue. If you are allowed to make changes and this is a recent occurrence then some recent change or addition is most likely the culprit.

Joe