Issue
An error screen while try to edit Office 2007 documents uploaded in SharePoint Document library. Unknown Error Trying To Lock File
This is mostly related to operating system and already been fixed in SP1, though sometimes we have to modify below registry settings.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters
On the Edit menu, point to New, and then click Multi-String Value.
Type AuthForwardServerList, and then press ENTER.
On the Edit menu, click Modify.
In the Value data box, type the URL of the server that hosts the Web share, and then click OK.
Exit Registry Editor.