Fossil undo doesn't work after a mv/ren operation.  Also, I'm unable to move the file back up the source tree because fossil thinks the path is outside of the checkout tree.  I tried several variations.  Here is my repro on Windows 7 using PowerShell:
<pre>
PS C:\rev\src\test> fossil ver
This is fossil version [7aae4ef068] 2010-09-03 01:57:41 UTC
PS C:\rev\src\test> fossil new ..\test.fossil
project-id: 642e99bc40ce3ba6e4b643dd79c1f8e14b55a645
server-id:  2fdbc1bdee11d946bba0105c34727630449caf84
admin-user: rwilso20 (initial password is "670296")
PS C:\rev\src\test> fossil open ..\test.fossil
PS C:\rev\src\test> ls


    Directory: C:\rev\src\test


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
-a---         10/6/2010  11:18 AM       7168 _FOSSIL_


PS C:\rev\src\test> echo 123 > x.txt
PS C:\rev\src\test> fossil add .\x.txt
ADDED  x.txt
PS C:\rev\src\test> fossil commit -m "1"
New_Version: aabc5e2eea1539d113322daa8a0395304c184a66
PS C:\rev\src\test> md sub


    Directory: C:\rev\src\test


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
d----         10/6/2010  11:20 AM            sub


PS C:\rev\src\test> fossil mv .\x.txt sub
RENAME x.txt sub/x.txt
PS C:\rev\src\test> fossil undo
c:\rev\bin\fossil.exe: no update or merge operation is available to undo
PS C:\rev\src\test> move x.txt sub
PS C:\rev\src\test> fossil mv .\sub\x.txt .
c:\rev\bin\fossil.exe: file outside of checkout tree: .
PS C:\rev\src\test> fossil mv .\sub\x.txt .\
c:\rev\bin\fossil.exe: file outside of checkout tree: .\
PS C:\rev\src\test> fossil commit -m "2"
New_Version: 910c565be0c6b70c70a0725eba977abec16837b5
PS C:\rev\src\test> ls


    Directory: C:\rev\src\test


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
d----         10/6/2010  11:21 AM            sub
-a---         10/6/2010  11:24 AM        211 manifest
-a---         10/6/2010  11:24 AM         41 manifest.uuid
-a---         10/6/2010  11:24 AM       8192 _FOSSIL_


PS C:\rev\src\test> fossil mv .\sub\x.txt .
c:\rev\bin\fossil.exe: file outside of checkout tree: .
PS C:\rev\src\test> fossil mv .\sub\x.txt .\
c:\rev\bin\fossil.exe: file outside of checkout tree: .\
PS C:\rev\src\test>
</pre>

fossil rename says 'file outside of checkout tree' when it isn't