Estou tentando instalar um pacote viadevtools::install_github pela primeira vez

l@np350v5c:~$ R --vanilla
> library(devtools)

Attaching package: ‘devtools’

The following objects are masked from ‘package:utils’:

    ?, help

The following object is masked from ‘package:base’:

    system.file

> search()
 [1] ".GlobalEnv"        "package:devtools"  "package:stats"    
 [4] "package:graphics"  "package:grDevices" "package:utils"    
 [7] "package:datasets"  "package:methods"   "Autoloads"        
[10] "package:base"

mas por exemplo

> install_github("devtools")
Installing github repo devtools/master from hadley
Downloading master.zip from https://github.com/hadley/devtools/archive/master.zip
Errore in function (type, msg, asError = TRUE)  : <not set>

A saída detraceback() é

> traceback()
12: fun(structure(list(message = msg, call = sys.call()), class = c(typeName, 
        "GenericCurlError", "error", "condition")))
11: function (type, msg, asError = TRUE) 
    {
        if (!is.character(type)) {
            i = match(type, CURLcodeValues)
            typeName = if (is.na(i)) 
                character()
            else names(CURLcodeValues)[i]
        }
        typeName = gsub("^CURLE_", "", typeName)
        fun = (if (asError) 
            stop
        else warning)
        fun(structure(list(message = msg, call = sys.call()), class = c(typeName, 
            "GenericCurlError", "error", "condition")))
    }(77L, "<not set>", TRUE)
10: .Call("R_curl_easy_perform", curl, .opts, isProtected, .encoding, 
        PACKAGE = "RCurl")
9: curlPerform(curl = handle$handle, .opts = curl_opts$values)
8: make_request("get", hu$handle, hu$url, config = config)
7: GET(url, config)
6: (function (url, name = NULL, subdir = NULL, config = list(), 
       before_install = NULL, ...) 
   {
       if (is.null(name)) {
           name <- basename(url)
       }
       message("Downloading ", name, " from ", url)
       bundle <- file.path(tempdir(), name)
       request <- GET(url, config)
       stop_for_status(request)
       writeBin(content(request), bundle)
       on.exit(unlink(bundle), add = TRUE)
       install_local_single(bundle, subdir = subdir, before_install = before_install, 
           ...)
   })(dots[[1L]][[1L]], dots[[2L]][[1L]], subdir = NULL, config = list(), 
       before_install = function (bundle, pkg_path) 
       {
           desc <- file.path(pkg_path, "DESCRIPTION")
           DESCRIPTION <- readLines(desc, warn = FALSE)
           if (any(DESCRIPTION == "")) {
               DESCRIPTION <- DESCRIPTION[DESCRIPTION != ""]
           }
           cat(DESCRIPTION, file = desc, sep = "\n")
           append_field <- function(name, value) {
               if (!is.null(value)) {
                   cat("Github", name, ":", value, "\n", sep = "", 
                     file = desc, append = TRUE)
               }
           }
           append_field("Repo", conn$repo)
           append_field("Username", conn$username)
           append_field("Ref", conn$ref)
           append_field("SHA1", github_extract_sha1(bundle))
           append_field("Pull", conn$pull)
           append_field("Subdir", conn$subdir)
           append_field("Branch", conn$branch)
           append_field("AuthUser", conn$auth_user)
       }, dependencies = TRUE)
5: mapply(install_url_single, url, name, MoreArgs = list(subdir = subdir, 
       config = config, before_install = before_install, ...))
4: install_url(conn$url, subdir = conn$subdir, config = conn$auth, 
       before_install = github_before_install, ...)
3: FUN("devtools"[[1L]], ...)
2: vapply(repo, install_github_single, FUN.VALUE = logical(1), username, 
       ref, pull, subdir, branch, auth_user, password, auth_token, 
       ..., dependencies = TRUE)
1: install_github("devtools")

Tentei com outro repo, mas ele se comporta da mesma maneira.

Alguma dica?

> sessionInfo()
R version 3.1.0 (2014-04-10)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=it_IT.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=it_IT.UTF-8        LC_COLLATE=it_IT.UTF-8    
 [5] LC_MONETARY=it_IT.UTF-8    LC_MESSAGES=it_IT.UTF-8   
 [7] LC_PAPER=it_IT.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=it_IT.UTF-8 LC_IDENTIFICATION=C       

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

other attached packages:
[1] devtools_1.5

loaded via a namespace (and not attached):
[1] digest_0.6.4   evaluate_0.5.1 httr_0.2       memoise_0.1    parallel_3.1.0
[6] RCurl_1.95-4.1 stringr_0.6.2  tools_3.1.0    whisker_0.3-2