error when using equation with text in plot to add greek letters

[ralmond]

I'm trying to add mathematical expressions to my plot using text(x,y,expression(...)). However, I'm getting a mysterious error message:

Warning: Error in text.default: invalid 'vfont' value [typeface -2147483648]

In the code samples below, the uncommented lines work as expected but the commented lines generate the error:
This part just sets up default values for the random numbers used later.

inputPanel(
  selectInput("M", label = "Number of Repetitions:",
              choices = c(50, 100, 200), selected = 100),
  
  numericInput("seed", label = "Random number Seed (integer)",
              min = 0, max = .Machine$integer.max, 
              value = floor(runif(1)*.Machine$integer.max), 
              step = 157)
)

renderText({
  M <<- as.numeric(input$M)
  set.seed(input$seed)
  Z <<- rnorm(M)
  paste("Number of Repetitions =",M,"Random Seed = ",input$seed,"\n")
})

Here is where the problem occurs

inputPanel(
  selectInput("N", label = "Sample Size:",
              choices = c(1,5,10,25,50,100), selected = 1),
  
  sliderInput("my", label = "Mean of Y:",
              min=0, max=100, value=50, step=1),
  
  sliderInput("sy", label = "Standard Deviation of Y:",
              min = 0.2, max = 25, value = 10, step = 0.1)
)

renderPlot({
  my <<- input$my
  sy <<- input$sy
  sem <<- input$sy/sqrt(as.numeric(input$N))
  X <<- Z*sem+my
  pch <<- floor(abs(Z))+1
  pch <<- ifelse(pch>2,5,pch)
  
  curve(dnorm(x,my,sem),xlim=c(my-3.5*sy,my+3.5*sy),ylab="density",
      xlab="Sample Mean")
  abline(v=my)
  abline(h=0)
  text(my+.25*sy,.02,expression(mu[Y]))
  abline(v=my-2*sem)
  text(my-2*sem+.25*sy,0.0025,expression(-2*sigma[bar(Y)]))
  abline(v=my-sem)
  #text(v=my-sem+.25*sy,0.0025,expression(-sigma[bar(Y)]))
  abline(v=my+sem)
  #text(v=my+sem+.25*sy,0.0025,expression(+1*sigma[bar(Y)]))
  abline(v=my+2*sem)
  #text(v=my+2*sem+.25*sy,0.0025,expression(2*sigma[bar(Y)]))
  points(X,rep(0,M),pch=pch)
})

renderText(
  paste("Standard Error = ",round(sem,3),":\n",
        sum(pch==1), "Estimates less than 1 SE from mean;\n",
        sum(pch==2), "Estimates between 1 and 2 SE from mean;\n",
        sum(pch==5), "Estimates more than 2 SE from mean.\n"))

I can't figure out why some of the expressions work and some do not. The differences are pretty small.

[ralmond]

Nevermind. I realized the problem is the v= in the text().

I'm feeling particularly silly right now.