This article discusses known issues that may occur with Office for Mac applications on MacOS 10.7 (Lion).

Note: Microsoft has been working with Apple from the early days of MacOS 10.7 (Lion). Through this partnership, many issues were addressed leading up to the Lion release. Microsoft will continue to work closely with Apple to address problems that may occur with Office for Mac 2008 and 2011 and Lion OS.

http://support.microsoft.com/kb/2586538