Why do I get some characters twice?

I have two GPIB devices connected to my computer. When I want to communicate with them using LV, I get a good response from the first one (Agilent 4278A Capacitance Meter), but not from the second one ("Hewlett Packard EPM-441A" Power Meter). Here is the detail. I send a "*IDN?" command. First one responds by sending its ID String, "HEWLETTPACKARD,4278A,0000A00000,REV3.31". When it comes to the second one, it responds as "HEEWLLLEETTTT--PPAACCKKAARRDD,,443377BB,,,,22..00​".
As you noticed, most of the characters are received twice. As I repeat the readings, the pattern changes a little bit, but again most of them are received twice.
So, my question is, do you have an idea why it happens? Is there a way to change/set communicati
on speed for LV's GPIB Read/Write objects?
I will appreciate your comments and helps. Thanks.
FYI, the VI is attached.
Attachments:
as1.vi ‏20 KB

Ahhh, very interesting. It sounds like you have two 488.2 drivers installed (except for the fact that both instruments don't respond with double characters even though they are connect to the same board, which is very strange)
I'd test if it happens when you use VISA and if NI-Spy shows the duplicate characters.
In any case, it's likely that something is indeed wrong with your installation. I'd bet that you have LabVIEW 6.0.2 or earlier, did a "complete" installation of LabVIEW, then later installed NI-488.2 separately.
Reinstallation Instructions:
*Remove All NI software through start -> settings -> control panel -> add/remove programs
*Open Windows Explorer and go to c:\program files, if there is a National instruments folder delete it and all of it's c
ontents
*Shut down the computer and remove the cards
*Install LabVIEW, do a custom install and cross out the NI-DAQ, VISA, and 488.2 drivers so they won't be installed
*Install 488.2 software
*Shut down and put in the GPIB card
All drivers can be found here
Regards,
Ray K

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