Weird behaviour by ordering a data frame

Your data frame contains lists, not vectors. You can convert this data frame to the "classical" format using as.data.frame and unlist:

df2 <- as.data.frame(lapply(df, unlist))

Now, the new data frame could be sorted in the intended way:

df2[order(df2[, 5]), ]

I've illustrated with a small example what's the problem:

df <- structure(list(ID = c(1, 2, 3, 4), 
          Latitude = c(50.7368, 50.7368, 50.7368, 50.7369), 
          Longitude = c(6.0873, 6.0873, 6.0873, 6.0872), 
          Elevation = c(269.26, 268.99, 268.73, 268.69), 
          Distance = c(119.4396, 119.4396, 119.4396, 121.199), 
          RxPower = c(-52.6695443922406, -52.269130891243, -52.9735258244422, 
                         -52.2116571930007)), 
          .Names = c("ID", "Latitude", "Longitude", "Elevation", "Distance", "RxPower"), 
          row.names = c(NA, 4L), class = "data.frame")

Notice that list only occurs once. And all the values are wrapped by c(.) and not list(.). This is why doing sapply(df, class) on your data resulted in all columns having class list.

Now,

> sapply(df, classs)
#       ID  Latitude Longitude Elevation  Distance   RxPower 
# "numeric" "numeric" "numeric" "numeric" "numeric" "numeric" 

Now order works:

> df[order(df[,4]), ]  
#   ID Latitude Longitude Elevation Distance   RxPower
# 4  4  50.7369    6.0872    268.69 121.1990 -52.21166
# 3  3  50.7368    6.0873    268.73 119.4396 -52.97353
# 2  2  50.7368    6.0873    268.99 119.4396 -52.26913
# 1  1  50.7368    6.0873    269.26 119.4396 -52.66954