Just re-flashed my Draytek 2600we router (from v 2.3.(something) to 2.5). Not straight forward, but seems to have fixed my "disconnected: corrupted MAC on input" problems.
When using ssh to my machine from the 'net, I used to get the odd "disconnected: corrupted MAC on input" problem. This was a pain because it would invariably happen when using "vi" or some such, which wouldn't die on the disconnect. Also, it was a pain because it disconnected ;-)
I've done quite a bit of trawling for a solution - apparently there are some fixes in OpenSSH, although using the latest version of the server didn't fix it. Apparently this can be due to dodgy cat5 cables, but I use wireless. It seems, it was actually due to dodgy firmware in my Draytek 2600we router.
The Draytek 2600 is a really good product. I really like it because "it does just what you want". Also, it's one of those products that you get, setup and use and then never have to touch again. It's well recommended, although don't expect a great manual ;-(
Anyway, there's new firmware, so I tried to upgrade. Following the instructions is pointless - it doesn't work. Looking at the newsgroups, it quickly became apparent that some voodoo was needed to actually get it to work. Here's an exerpt from James Hebben's post, describing what he (and I) did to get it to work:
1. Disconnected the ADSL line from the router
2. Disabled the Wireless network connection from my PC
3. Connect the LAN cable between the router and my PC
4. Set the IP manually to 192.168.1.11
5. Set the subnet mask to 255.255.255.0
6. Set the default gateway to 192.168.1.1
7. Run the Router Tools | Firmware Upgrade Utility
8. Enter the router IP address 192.168.1.1
9. Browse for either of the two downloaded upgrade files
10. Powered off the router
11. Press the factory reset button
12. Powered on the router
13. Waited for the two leftmost LEDs to begin flashing
14. Release the factory reset button
15. Hit the send button
(which worked for me). The pre-reqs being you have to use an old version of the router tools.
Oh, after you do all this, you have to reconfigure your ADSL and router settings all over again (restoring a backup looks like a bridge too far).
UPDATE: This fix has had a very positive effect on connections to my web server (behind the Draytek) from the Internet. Previously, the odd connection would timeout for no apparent reason, but a retry would always work. Now, it all seems to be pretty perky and reliable.