It's already happened to me a few times. Two smbd processes seem to be spinning endlessly, writing zounds of following messages to syslog:
Jul 19 21:59:43 omoikane PAM_smbpass: Failed to find entry for user UTF-16LE.
And before that a single:
Jul 19 21:59:43 omoikane PAM_smbpass: Failed to find entry for user nobody.
The only other computer in my network is a Windows 98 machine. This has started once "Network Neighbourhood" had been opened.
I run samba 3.0.24 on a 64-bit Gentoo box. Package version is -r3. You can see my smb.conf at http://kolos.math.uni.lodz.pl/~grzywacz/smb.conf.