Apple released Mac OS X 10.5.1 and Mac OS X Server 10.5.1 updates for Leopard. Release notes:  

AirPort

• Allows password-protected accounts on AirPort Disks to show up on in the Finder’s Shared Sidebar.
• Resolves an issue with saved passwords for wireless networks.

Back to My Mac

• Improves the reliability of Back to My Mac-enabled Macs appearing in the Finder’s Shared Sidebar.
• Improves compatibility with D-Link NAT gateways.

Disk utilities

• Restores the functionality of the progress bar during permission repairs in Disk Utility.
• Addresses an issue that could produce an alert when creating disk images using Disk Utility or Terminal.
• Improves disk partitioning when multiple RAID sets are created on the same disk.

iCal

• iCal alarms are now more reliably delivered via email.
• Resolves an issue when inviting attendees via a CalDAV account.

Mail

• Improves stability when resizing columns in the message viewer or switching between Stationery templates in email messages.
• Addresses an issue in which attachments enclosed inside an HTML link may not be clickable in email messages.
• Fixes an issue with email accounts added using the “Simple Setup” feature in which messages cannot be sent due to an SMTP connection failure.
• Improves Smart Mailboxes compatibility with .Mac Sync, and addresses an issue with To Do’s disappearing when using Smart Mailboxes.
• Resolves an issue with syncing Mail accounts with .Mac in which multiple On My Mac folders appear in the Mailbox pane.

Networking

• Addresses an issue in which Microsoft Windows shared folders may be read-only when connected via SMB.

Printing

• Resolves an issue in which user-selected values on Paper Feed PDE are reset to default while saving a custom preset.

Security, Firewall

• Addresses a code signing issue; third-party applications can now run when included in the Application Firewall or when whitelisted in Parental Controls.
• In Security preferences’ Firewall tab, the “Block All” option is now called “Allow Only essential services”
• Includes recent Apple security updates.

System and Finder

• Addresses a potential data loss issue when moving files across partitions in the Finder.
• Resolves an issue with login after turning off FileVault for a specific user account.
• Improves compatibility with Adobe Flash-based uploaders used by .Mac Web Gallery and certain other websites and applications.
• Resolves a potential text drawing issue with certain Adobe Flash-based websites and applications.

Time Machine

• Addresses formatting issues with certain drives used with Time Machine (specifically, single-partition MBR drives greater than 512 GB in size as well as NTFS drives of any size and partition scheme).
• Resolves an issue in which files restored in Time Machine may be restored to the backup hierarchy rather than the folders to which they belong.