Same problem as well.
No solution, but here's an interesting thing: For me, "curl" and "wget" are also broken in exactly the same way. This makes me wonder if it is one of the underlying networking libraries (libcurl, or similar) that is at the root of the problem (total guess).
EDIT: I have solved this problem. The problem turned out to be what seems to have been a "bad" version of openssl. I used the Cygwin setup program to "Reinstall" OpenSSL. The version number in setup is now "0.9.8n" which seems to have replaced "0.9.8", which I suspect was a bad version that was temporarily distributed, so if you were unlucky enough to update at the wrong time then this is what you got. The new version doesn't seem to be installed automatically just by updating normally. I'm guessing 0.9.8 is seen as the same version as 0.9.8n.
In case this doesn't solve it for others: the key insight was gained by launching svn.exe from Windows Explorer. While it exits silently when run from the bash command line, when run from Windows Explorer it pops up a window complaining: "the procedure entry point pqueue_size could not be located in the dynamic link library cygcrypto-0.9.8.dll". This allowed me to identify OpenSSL as the culprit. The same might be possible for other problems that manifest as commands silently exiting when run from the bash terminal.