R shiny dashboard, markdown knitr::kable grid lines are gone after upgrade

I have R shiny dashboard application in which I render a R Markdown document ( it uses knitr::kable function to print a data table ) and include the resulting application using includeHTML in server.R and render it using uiOutput in ui.R

Recently upgraded packages to ( knitr : 1.12.3 ; shiny dashboard : 0.5.1 )

Now the rendered table in the shinydashboard output doesn't have grid lines, I'm not sure what caused it - any ideas?

Here is the relevant portion of the code from server.R :

 output$sae_text<-renderUI({
          req(input$sae_userids)
          render('myrmd.Rmd',output_dir=".",output_file="temp.html",params=list(subject=input$sae_userids))
          includeHTML("temp.html")
    })  

Here is the relevant portion of the code from myrmd.Rmd :

 ```{r, results='asis',echo=FALSE}
  knitr::kable(ex4)}
 ```

Here is the relevant portion of the code from ui.R :

  tabItem(tabName="SAE",
          fluidRow(box(width=12,uiOutput("sae_text"))),
          ),