My belief would be that nobody else in your household is using half the traffic you are. That's a lot of bandwidth to be trying to consume between those two applications. Do you happen to know what speed your connection is?
If not, I suggest you go to
SpeedTest.net/ and run their speed test, and report the results.
But Skype often fails even when I'm not using Minecraft... so I'm not sure if that's the problem.
Even so, my internet is crap.
http://www.speedtest.net/result/1207050693.png
Yesterday, the download speed was just over 2MB...
Besides, it used to work fine, so I don't understand.
You are having a series of issues all coming together it sounds like ehre
A woreless connections are known to constantly drop/reconnect expecially when under heavy use. If you can not wire it directly check out DD-WRT and once installed you can use a Linksys [or other router they support] in the room where the comp is to wirelessly connect to the router you use for the internet and then use a cable from the router with DD-WRT to the computer. I switched from wireless to this setup a couple years ago and have noticed HUGE gains in stability and speed [I now have two wireless antennas instead of one not to mention routers are setup to transmit and receive with much higher power]. Then after you do that you will also want to port forward Skype's ports to your machine specifically as Skypes seems to always have issues with NAT.
You could also make sure the person hosting the call is the one with the fastest upload and download speeds as some skype calls will have issues if the machine being used to host the call can not keep up with the other computer [and your gaming as well]
ALSO I would recommend you try another program built-in for gaming and talking while gaming specifically [I know there is Raptr [part of Steam and Free] I think there is RaidTalk that is popular. You may also want to check Skype and or MineCraft Settings [does it allow you to specify lower audio quality for your skypwe call [view advanced audio settings and if it mentions bit-rate, try choosing a lower bit-rate [128KBps is CD Quality you could prolly do something like even 56KBps [roughly good FM Station quality] and still have fine audio.
Also, you could get in to QOS [Quality of Service] settings if your router has them. This would allow you to say if there is data coming in on this port or from this address or has this type of data I want you to try to give it priority and drop other connections, but keep a certain amount of bandwidth open for this type deals.
Also go in to your network center, click to change adapter settings, click advanced tab and check for things like is it set to a low power setting? CHANGE THAT, is it set to turn off if comp goes to sleep CHANGE THAT, is it set to something less than 54G CHANGE THAT, etc [you get the point].
Finally Finally check out speedguide.net under broadband or tools for their TCP Optimizer. Once downloaded you can tweak all the registry settings to help Windows get the best speed out of your network [it is pretty good at helping non-tech users as well it has a slider you can set to your ISP speeds and it will set suggested settings.