Error using twitter R package's userTimlien
It seems to be working well on my configuration:

Ubuntu Vivid and R:

&gt; sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-pc-linux-gnu (64-bit)

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

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

other attached packages:
[1] twitteR_1.1.8

loaded via a namespace (and not attached):
 [1] bit_1.1-12     bit64_0.9-4    bitops_1.0-6   DBI_0.3.1      httr_0.6.1    
 [6] magrittr_1.5   RCurl_1.95-4.6 rjson_0.2.15   stringi_0.4-1  stringr_1.0.0 
[11] tools_3.1.2  


Maybe you should update packages versions?