This is the capacitor I recently had to remove from my Mikrotik RouterBOARD 750G:
As you can see, it is a Su’scon 560µF capacitor. There is at least one thread about bad caps on routerboards on the Mikrotik support forums, they generally seem to be aware of it and it might not be a problem on newer versions.
To fix the problem I salvaged a 1000µF capacitor from an old motherboard and it seems to do the trick.
Update (May 2015):
Since people keep visiting this blog post, the Routerboard with the replacement capacitor is still going strong and has been routing my internet traffic for 2.5 years since replacing the cap.