On 16.06.2011 Microsoft fixed an Security Issue with Samba which ended in Windows Users beeing unable to access Unix Samba Shares by using Plain Text Authentication.
By removing Security Update KB2536276 and rebooting you can enable your client again - or you patch your samba server, which is the real source of error - Microsoft did just fix an flaw.

https://bugzilla.samba.org/show_bug.cgi?id=8238

https://bugzilla.samba.org/attachment.cgi?id=6593

Infos taken from:
http://answers.microsoft.com/en-us/windows/forum/windows_xp-windows_update/kb2536276-windows-xp-pc-get-system-error-58-when/d9dbdde5-2666-4423-b47c-fbdb80b995d9