Access SQL Update Error: "No value given for one or more required parameters."

Hello,
From a C# program, using OleDb, I can do an insert into an Access db with no problem. But then when I go to update a row I've inserted I get this error:
"No value given for one or more required parameters."

Here are my insert and update statements:

"Insert Into Appt ( ApptID, ApptDate, StartTime, EndTime, CustID, CustName, EmpID, EmpName, Location, ApptNotes, Estimate) Values ( 'f5ce3d7a-be4b-4cfa-985b-a76e667b0982',#4/27/2004 12:00:00 AM#, 12, 14, '60000-1081872920', 'Lindsay:Test Job 1', '650000-1042121023', 'Duncan Fisher', \"\", \"\", 0)"

"Update Appt Set ApptID = 'f5ce3d7a-be4b-4cfa-985b-a76e667b0982', ApptDate = #4/27/2004 12:00:00 AM#, StartTime = 12, EndTime = 13, CustID = '60000-1081872920', CustName = 'Lindsay:Test Job 1', EmpID = '650000-1042121023', EmpName = 'Duncan Fisher', Location = \"\", AppNotes = \"\", Estimate = 0 Where ApptID = 'f5ce3d7a-be4b-4cfa-985b-a76e667b0982'"


And my Table:
Appt:

ApptID Text
AppDate Date/Time
StartTime Number
EndTime Number
CustID Text
CustName Text
EmpID Text
EmpName Text
Location Text
ApptNotes Text
Estimate Yes/No
DeviceID Text
DeviceApptID Text

The only required field is ApptID, and all of the Text fields (besides ApptID) allow zero length.

Any ideas/suggestions?

Thanks,
Lindsay