getdata giving "An unexpected error occurred."

Occassionally I'll get an error when I make a getdata call. Here is the sample code and the error it throws.

Code:

[DAQ_data, DAQ_time] = getdata(ai, ai.SamplesAcquired);

Error:

??? An unexpected error occurred.

Error in ==> analoginput.getdata at 199
    [varargout{1:nout}]=getdata(uddobj,samples,dataformat);

Anyone seen this before and have any recommendations on fixing it?

Thank you!

[Sean de Wolski]

Everything's plugged in and has been plugged in since the beginning of the ML session?

[Adam]

Yep -- I'm doing multiple getdata calls in the same ML session/script.

[Adam]

Between getdata calls the only calls I'm making to my ai object are start() and stop().