Skype can't connect - most likely router problem, ...

Question

Lately I can't connect to Skype at home. I've tried a lot of different solutions but none of them work.
The problem started a few months ago when I just couldn't sign into Skype (can't connect). At that time I had no change in any network settings on my computer nor my router. Interestingly enough, I could connect to Skype on Ubuntu (I have dualboot). Though even Ubuntu eventually failed to connect back then (just can't sign in) - still no changes in my network. I couldn't be bothered at the time with the problem so I just didn't use Skype.
However after some time (some weeks or a month or two), when I tried to connect to Skype again, it worked (on Win 7 as well as Ubuntu). Again, no changes to my network have been done in the mean time (Skype might of been updated, but I doubt it was on both platforms at the same time).
So Skype worked for a while until about a month ago, when the problem reoccurred. This time I said I'm going to get to the bottom of this so here is the situation:
I can connect to Skype at work no problem (on my desktop as well as my Android phone)
I can't connect to Skype at home (just won't sign in) on my desktop nor my phone
I have tried:
Reinstalling Skype with cleaning everything that Skype might have left behind
Installing an (a bit) older version 6.9 (because even the latest 6.11 didn't work). Though these two attempts I've come to see are in vain once I figured out that I can't connect to Skype on my phone as well.
Resetted my router a couple of times.
Reset my router settings to default.
Opened/forwarded Skype ports to my (local) IP. I even enabled DMZ to redirected all traffic to my desktop computer (although I'm not 100% sure that that worked as I imagine it should work).
Tried some proxy settings in Skype (Connection options) I found on your forum.
None of the above worked in any way...
My router is a TP-Link TL-WR1043ND with (I think the latest) firmware version 3.13.13 Build 130428 Rel.58290n (hardware is v1).
TLDR:
I can't sign in to Skype at home. It works when I'm at work. I can connect to Skype on my phone if I'm at work (over WiFi) or if I'm on 3G, but not if I'm on my home WiFi. That said, no software firewall can be the problem here, but my router. However I have no more ideas as to what else I can try. This forum is my last hope for finding a solution.
Please help.
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Answer 1

I do not know the makeup of Skype's internal security policies when it comes to this as they are not too open about this. Most companies are not. These are the only reasons I believe a block would occur based off any company's security policy.
1. A proactive measure - A blacklist of IPs is constantly obtained/updated to include anonymizer services that might harm the network.
2. An active/counteractive measure -
I. Someone uses an anonymizer to SPAM people on the Skype network:
a. Users complain using the abuse option. Users get the IP Auto-banned.
b. The company (Skype) receives the complaints or notices a trend and Manual/Auto bans the IP.
II. Too many people (connections) sign on with the same IP (due to an exit relay/proxy). Due to this being very suspicious, (maybe even DDos-like behavior) the IP is Auto-banned.
I tend to lean more towards the counteractive measure since I don't believe many proactive measures are needed to limit abuse. There is always at least one rotten apple that engages in illegal activity using anonymizers, proxies, etc. that ruin it for everybody. In reality I believe it is a combination/balance of the two. Not to be prejudice against anonymizers, just blacklists to protect the network from known attacks. For whatever reason once the threshold is met, the IP is banned.  If I had to guess how long it would be in intervals of 30 days (30, 60, 90, 120, etc.). The whole Internet is not going to banned so the security policies in effect can't be too strict. It's goal is probably just to limit the majority of bad behavior that causes problems for their customers.
Skype is not the only service that reacts this way. Even ISPs will receive notices and in turn will send notices to their customer that since illegal activity (RIAA notices, etc.) is occurring due to a Tor exit relay or some other anonymizer, the ISP will terminate services with that customer if they don't cease (due to breach of contract).
I don't know whether you can limit an exit relay so it can't be used to access Skype. It may be a lost cause. If I made the choice to run a similar service it would be with a whitelist of people I knew who wouldn't use it to perform illegal activity, just remain anonymous when online.
You shouldn't have any issues running a non exit relay since in doing so your IP is not being broadcast all over the Internet like a calling card which an exit relay does. Changing your modem's MAC address is something you need to call your ISP for. However changing your router's MAC address generally does not require that. All that is required is a reboot of the modem, router, and possibly computer if you run into issues. You will probably continue to run into the same problem as long as you attempt to run an exit relay.
Be aware that for every IP that get's banned on your ISP is another IP a person could get issued for 24 hours to a week + after it gets released. Some people then visit this community and complain how they can't connect when it worked not too long ago and how Skype "sucks". So sometimes things like this create a ripple effect for other customers.