The H-Factor

In 2010, xref'd layers are shown faded by default. According to JTB World there is a new AutoCAD variable that controls that: XDWGFADECTL

Go to tools > options > display tab > and at the bottom right corner find FADE CONTROL. Under it is xref display.

Or, type it in, and set it as you desire (from AutoCAD sysvar reference):

XDWGFADECTL

Controls the dimming
for all DWG xref objects.

The valid XDWGFADECTL
system variable value is between -90 and 90. When XDWGFADECTL is
set to a negative value, the Xref Fading feature is not turned on,
but the setting is stored.

This and a list of other new 2010 variables can be found at JTB World New 2010 Variables