Error with LuaRocks on Lua for Windows

["Stuart P. Bentley" <stuart@...>]

After extracting the LuaRocks for LfW zip over my desktop's LfW 5.1.4-34  
installation, I was able to install wsapi-xavante just fine. However, my  
friend who extracted it over his LfW 5.1.4-35 installation had this error:

C:\Users\Charlie>luarocks install wsapi-xavante
Installing  
http://luarocks.org/repositories/rocks/wsapi-xavante-1.3.4-1.win32-x8
6.rock...

Error: Failed unpacking rock file:  
C:\Users\Charlie\AppData\Local\Temp\luarocks_
luarocks-rock-wsapi-xavante-1.3.4-1-2472/wsapi-xavante-1.3.4-1.win32-x86.rock

(Also, his changes.txt file says 5.1.4-34 at the beginning of the 5.1.4-35  
changes section.)

On my tablet running LuaRocks extracted over Lua for Windows 5.1.4-37, I  
get this error:

C:\Users\Stuart>luarocks install wsapi-xavante
Installing  
http://luarocks.org/repositories/rocks/wsapi-xavante-1.3.4-1.win32-x8
6.rock...

Missing dependencies for wsapi-xavante:
xavante >= 2.2.0
rings >= 1.2.3
wsapi >= 1.3.4
coxpcall >= 1.13


Missing dependencies for xavante:
copas >= 1.1.5


Missing dependencies for copas:
coxpcall >= 1.13


Error: Failed installing dependency:  
http://luarocks.org/repositories/rocks/xava
nte-2.2.0-1.all.rock - Failed installing dependency:  
http://luarocks.org/reposit
ories/rocks/copas-1.1.6-1.all.rock - Failed installing dependency:  
http://luaroc
ks.org/repositories/rocks/coxpcall-1.13.0-1.all.rock - File already  
exists: C:\P
rogram Files (x86)\Lua\5.1\lua/coxpcall.lua