I have exactly the same problem as detailed here New release candidates for MapWinGIS and MapWindow5 are available:
User tile requests are sometimes crashing, I think I’ve seen it with other providers but definitely Open Street Maps. As I say, basically the same as the above thread details. I am using 5.3 64-bit and I believe the fix for the problem has only been put into the 32-bit build.
Looking at the two installations - 32-bit libcurl.dll has no dependency on libeay32.dll anymore, but the 64-bit does.