Apple this week issued a sixth beta of its Mac OS X 10.6.4 security and maintenance update for its Snow Leopard operating system. Per AppleInsider, the latest build remains free of known issues.

According to sources close to the story, the beta, which was issued to developers last Tuesday, is labeled as “build 10F564″, weighs in at 600 megabytes which developers being asked to focus on graphics drivers, SMB, USB, VoiceOver and VPN.

The last few builds have all contained the same focus areas and enhancements, and this week’s update is no different. The updates addressed issues that could cause the keyboard or trackpad to become unresponsive, and also fixed a problem that prevented some Adobe Creative Suite 3 applications from loading.

Apple first began widespread testing of Mac OS X 10.6.4 in late April. The previous update to Snow Leopard, Mac OS X 10.6.3, was released at the end of March. It included improvements for QuickTime X and OpenGL-based applications, in the form of a 437.2 megabyte update.