Build R package on Mac for Windows - r

Question

I develop a package under Mac and want to distribute it to my colleagues. I can build the package under Mac and can install it under Mac and 'most' of my colleagues Windows PCs. Some of these are Windows 7 and some are Windows 8. All of them use RStudio and different R Versions all above 3.1.
I have now one big Problem with one computer and can not figure out what to do.
When I try to install the package, I get the following message
install.packages("C:/Users/ncasasvi/Downloads/imbproteomicsr_0.1.6.tar.gz", repos = NULL, type = "source", lib="\\fs02/ncasasvi$/Dokumente/R/R-3.1.2/library")
Warning in install.packages :
'lib = "\fs02/ncasasvi$/Dokumente/R/R-3.1.2/library"' is not writable
'\\fs02\ncasasvi$\Dokumente'
CMD.EXE was started with the above path as the current directory.
UNC paths are not supported. Defaulting to Windows directory.
'\\fs02\ncasasvi$\DOKUME~1\R\R-31~1.2' is not recognized as an internal or external command,
operable program or batch file.
Warning in install.packages :
running command '"//fs02/ncasasvi$/DOKUME~1/R/R-31~1.2/bin/x64/R" CMD INSTALL -l "\\fs02\ncasasvi$\Dokumente\R\win-library\3.1" "C:/Users/ncasasvi/Downloads/imbproteomicsr_0.1.6.tar.gz"' had status 1
Warning in install.packages :
installation of package 'C:/Users/ncasasvi/Downloads/imbproteomicsr_0.1.6.tar.gz' had non-zero exit status
I copied now the complete package source, so all folders and files, to a Windows machine, installed Rtools and devtools there and build the package on the windows machine with the same problem...
Is there a way to geht a more precise error message, not just status one? I have no further Ideas.
I also sensed my file to win builder. It reported no error messages, but I also didn't got a 'new build package' from the website.
Hope some of you have some suggestions. Thanks in advance!
EDIT:
After changing the path to something without \\ at the beginning and trying to get rid of all the other error messages, I got this message:
> install.packages("C:/Users/ncasasvi/Downloads/imbproteomicsr_latest.tar.gz", repos = NULL, type = "source", lib=('U:/Dokumente/R/win-library/'))
Error: ERROR: no packages specified
Warning in install.packages :
running command '"C:/PROGRA~1/R/R-31~1.2/bin/x64/R" CMD INSTALL -l "U:\Dokumente\R\win-library\" "C:/Users/ncasasvi/Downloads/imbproteomicsr_latest.tar.gz"' had status 1
Warning in install.packages :
installation of package ‘C:/Users/ncasasvi/Downloads/imbproteomicsr_latest.tar.gz’ had non-zero exit status
In between, I had a partly success, but it still could not install the package. This was the output in between:
> install.packages("C:/Users/ncasasvi/Downloads/imbproteomicsr_latest (2).tar.gz", repos = NULL, type = "source")
Installing package into ‘\\fs02/ncasasvi$/Dokumente/R/win-library/3.1’
(as ‘lib’ is unspecified)
'\\fs02\ncasasvi$\Dokumente'
CMD.EXE was started with the above path as the current directory.
UNC paths are not supported. Defaulting to Windows directory.
* installing *source* package 'imbproteomicsr' ...
** R
** data
*** moving datasets to lazyload DB
** preparing package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded
*** arch - i386
Warning in library(pkg_name, lib.loc = lib, character.only = TRUE, logical.return = TRUE) :
no library trees found in 'lib.loc'
Error: loading failed
Execution halted
*** arch - x64
Warning in library(pkg_name, lib.loc = lib, character.only = TRUE, logical.return = TRUE) :
no library trees found in 'lib.loc'
Error: loading failed
Execution halted
ERROR: loading failed for 'i386', 'x64'
* removing '\\fs02/ncasasvi$/Dokumente/R/win-library/3.1/imbproteomicsr'
Warning in install.packages :
running command '"C:/PROGRA~1/R/R-31~1.2/bin/x64/R" CMD INSTALL -l "\\fs02\ncasasvi$\Dokumente\R\win-library\3.1" "C:/Users/ncasasvi/DOWNLO~1/imbproteomicsr_latest (2).tar.gz"' had status 1
Warning in install.packages :
installation of package ‘C:/Users/ncasasvi/DOWNLO~1/imbproteomicsr_latest (2).tar.gz’ had non-zero exit status