Mac Mini Ethernet SSL connection issues

Question

Hi,
Up until recently I have been using my Late 2012 Mac mini with a WiFi connection. Recently though I've had reason to switch to a Gigabit Ethernet connection (short version, moved from UK to Canada, living with in-laws and they have a crappy wireless router that can't hold a stable connection for more than a few hours).
However, I'm getting a really odd Ethernet network issue where my mac will "corrupt" SSL connections. This normally manifests itself in web pages not fully downloading, images becoming corrupted, or errors when downloading files. The last one is particularly hurting as I have been doing some heavy downloading of DMG files and other installers, all of which are a 100% guaranteed fail with DMG files reporting as being corrupted if I try to open them.
I have also lost my time machine backup as OSX has reported that this has failed verification and needs to be created new; I accepted creating a new one (reluctantly) and the backup now fails to complete every time it runs - either the wireless cuts out or the SSL connection corrupts the backup.
I have a 16-port GigE Switch (Netgear GS116) with a number of computers and the home modem plugged into this.
I've tried the following to look at this:
I've tried (and tested) a number of different Cat5e and Cat6 cables. These all work fine with other Windows / Linux machines and according to my cable tester all check out. 100% of the cables I own produce the error leading me to believe that it's not a cable problem.
Problem occurs even if the switch is bypassed and the mac plugged directly into the modem.
Problem does not occur (for web pages and small downloads) when plugged into wireless - this is just sloooow and as the router seems to develop issues with DNS over WiFi, I have to reset it every few hours so long term downloads fail.
I found an article (which I have now lost the URL for) where someone suffered intermittent network issues with Ethernet that they resolved by un-checking the "Enable automatic connection" on the 802.1X page of the network settings. This appeared to help for a couple of days and I enjoyed fast Ethernet and downloads once more. However, today the problem is back in force.
I am able to download files from a windows machine (well, except for downloads via the App store) and then transfer them over the network to the mini with no problems at all - the corruption issue only seems to occur when SSL is involved.
So I'm wondering what it could be and how I would go about diagnosing the issue. I'm more familiar with Windows / Linux systems, having not owned a Mac since the days of System 7 - the mini was bought so I could play with learning XCode and try my hand at Mac software development.
Thanks in advance,
~MrBasset.
Machine specs:
Late 2012 Mac Mini running OXS Mavericks 10.9.3
2.5Ghz Intel Core i5
16GB Ram

Answer 1

Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
The title of the Console window should be All Messages. If it isn't, select
          SYSTEM LOG QUERIES ▹ All Messages
from the log list on the left. If you don't see that list, select
          View ▹ Show Log List
from the menu bar at the top of the screen.Click the Clear Display icon in the toolbar. Then try the action that you're having trouble with again. Select any messages that appear in the Console window. Copy them to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.
The log contains a vast amount of information, almost all of which is irrelevant to solving any particular problem. When posting a log extract, be selective. A few dozen lines are almost always more than enough.
Please don't indiscriminately dump thousands of lines from the log into this discussion.
Please don't post screenshots of log messages—post the text.
Some private information, such as your name, may appear in the log. Anonymize before posting.