Linksys Wireless Router :: WRT54GC Dropping Internet Connection

I've been using my Linksys WRT54GC for couple years now, and only recently have I started to have significant issues with the device. I'm using a 2012 Macbook Pro, and my internet connection seems to be randomly dropping every now and then. Sometimes it works just fine for couple of hours only dropping once or so, sometimes it starts dropping literally every few seconds. What I usually do is quickly restart my wifi and the connection comes back right away. I also tried not doing that, and the internet connection tends to come back up after a minute or so. 
 
I have read countless topics, also tried many things: changing MTU, the thresholds in router settings, security modes (it seemed to have worked fine after I changed it to WPA, not anymore though. I'm using no password now and it doesn't fix the problem either), changing the channel (my strongest signals around are on channel 1 and 11, thus I left mine on 6), I even reset the router today (held the reset button for 10 seconds~) but it didn't work either. I didn't upgrade the software since I heard stories about the software available on this site being corrupted or something, bricking the router, which is the last thing I'd want (I'm running on 1.00.7 now).
 
I have the impression (but it's just an impression, it might as well not be the case, and just me trying to find out when it happens, since it's not always that it breaks the connection while doing that) that it breaks the connection on high load, I mean when I'm for example using skype and facebook, and then try to go on reddit at the same time - the reddit webpage won't load, and the connection is lost after few seconds. But it also started dropping every few seconds while I was playing an online game and skyping at the same time today, which isn't a particularly huge problem for a 23Mbps download and 1.5 upload speed internet I suppose, and which it never did before. I have never had such issues with my PC using a Linksys USB adapter. The connection would drop from time to time when, for example, accidentally going on pages with lots of thumbnail pictures, or trying to load 15 tabs of jpgs at the same time, it was never that much of a problem really though, I just thought it's normal.