Read() fails immediately with any extra parameters

[emkman]

I am trying to read in a 10 digit phone number.
Read(toNum) works fine, however Read(toNum, , 10) immediately hangs up the call. I don't think my syntax is wrong based on the docs, and the log indicates that it understood the maximum digits parameter:

[Feb 21 07:01:11] VERBOSE[16514] logger.c: -- Accepting a maximum of 10 digits.

However, it always fails with a file read error involving the second parameter, which is the recording to play.

[Feb 21 12:12:47] WARNING[17222] file.c: File does not exist in any format
[Feb 21 12:12:47] WARNING[17222] file.c: Unable to open (format 0x4 (ulaw)): No such file

I was not trying to play a file, but i have tried adding one to make it happy. Taking a standard sound 'beep' from the default sounds directory, I can say
Playback(beep) and the sound will play. On the next line, if I say Read(toNum, beep, 10) , I get

[Feb 21 07:01:11] WARNING[16514] file.c: File beep does not exist in any format
[Feb 21 07:01:11] WARNING[16514] file.c: Unable to open beep (format 0x4 (ulaw)): No such file or directory

Any thoughts on why my Read command is barfing?