I have a lot of experience hunting bugs that make no sense, sometimes in my own code and sometimes in other people's. I usually find it harder to find those bugs in my own code, and it certainly isn't because my code is particularly "clever".
The common pattern that I find in "bugs that make no sense" is that I am believing something that isn't true. Once I identify and challenge that belief, the bug becomes obvious. The reason that these bugs are harder to find in my own code is because I believe my code is correct (in general, and in lots of specifics), so I don't question it so closely. When I'm reading other people's code I have less belief that it is correct, so less hindrance to finding the bugs.
Put another way: finding a bug in my code is both a success and an admission of failure. Finding a bug in someone else's code is pure success. This sounds like a strong case for pair-programming!