Error to access folder in RStudio server when using snowfall

Question

I am using RStudio server and snowfall. My parallel codes always give me these messages:

> sfInit(cpus = 14, parallel = TRUE)
> sfLapply(seq(along = trials), nvtPar, file)
23 Nov 2014 11:31:36 [rsession-users] ERROR svn: E070008: Can't read directory 'my-current-working-directory': Partial results are valid but processing is incomplete
; LOGGED FROM: core::Error session::modules::svn::status(const core::FilePath&, std::vector<session::modules::source_control::FileWithStatus, std::allocator<session::modules::source_control::FileWithStatus> >*) /home/ubuntu/rstudio/src/cpp/session/modules/SessionSVN.cpp:809

In my parallel function (nvtPar), I read a few files from hard drive and write a file into hard drive. All files are in the sub folder.

This server builds on a VMware virtual server with 16 cores. My working directory is nfs server and mounted as my home directory.

My RStudio server is Version 0.98.994.

This is my session information:

> sessionInfo()
R version 3.1.1 (2014-07-10)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C         LC_TIME=C            LC_COLLATE=C         LC_MONETARY=C        LC_MESSAGES=C        LC_PAPER=C          
 [8] LC_NAME=C            LC_ADDRESS=C         LC_TELEPHONE=C       LC_MEASUREMENT=C     LC_IDENTIFICATION=C 

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] snowfall_1.84-6       snow_0.3-13           magrittr_1.0.1        XML_3.98-1.1          ncdf4_1.13 dplyr_0.3.0.9000

loaded via a namespace (and not attached):
[1] DBI_0.3.1           Rcpp_0.11.3         assertthat_0.1      lazyeval_0.1.9.9001 parallel_3.1.1      tools_3.1.1        

Thanks for any suggestions. Please let me know if my question is not clear.

EDIT: As suggestions by @roman-luštrik, I added my minimum example to reproduce my question (Sorry I cannot post my whole script, but this example will produce the same error message).

trials <- seq(1, 1593)
nvtPar <- function(i, file)
{

    # Generate the random string which will store in the disk
    MHmakeRandomString <- function(n=1, lenght=12)
    {
        randomString <- c(1:n)                  # initialize vector
        for (i in 1:n)
        {
            randomString[i] <- paste(sample(c(0:9, letters, LETTERS),
                                     lenght[i], replace=TRUE),
                                     collapse="")
        }
        return(randomString)
    }
    sim <- MHmakeRandomString(2553, round(runif(2553) * 344))
    write.table(sim, file = paste0(i, '.sim'), 
                                quote = FALSE,
                                row.names = FALSE,
                                col.names = FALSE)
    # Do some calculation
    Sys.sleep(0.213 * (1 + (runif(1) * 2 - 1)) * 0.4)
    # Remove the temp file
    file.remove(paste0(i, '.sim'))
    # Do other calculaation
    Sys.sleep(2.32 * (1 + (runif(1) * 2 - 1)) * 0.1)

}

library(snowfall)
sfInit(cpus = 14, parallel = TRUE)
a <- sfLapply(seq(along = trials), nvtPar, file)
sfStop()

After digging, it seems this error is related with file.remove in the parallel calculation. All errors will disappear if I comment this line:

file.remove(paste0(i, '.sim'))

BTW: I use svn for version control in the working directory.