Hello-
Still odd: I tried it with the same version of the PowerGUI ScriptEditor (v3.6.0.21), and it succeeded with one-, two-, more rows in the CSV file.
I have seen issues before where the PowerGUI ScriptEditor console does not quite behave like a regular PowerShell console, but I am not convinced that is the issue here. To further test that: how do these commands behave when you issue them in a regular PowerShell console (outside of PowerGUI ScriptEditor)?
And, what is the error message that you receive when the Import-Csv or ConvertFrom-Csv calls fail?