An alias is just a name that you assign to a VISA Resource. For example, the actual VISA Resource name for a GPIB instrument might be GPIB0::3::INSTR. This means that a GPIB instrument with the address of 3 was found connected to the GPIB0 controller. The resource name is visible when you right click on the GPIB board in MAX, select Scan for Instruments, and then highlight the instrument(s) that the scan finds. You can assign a more meaningful name to that instrument; i.e. DMM. The more meaningful name is the alias. You don't need to assign an alias.
It sounds like your problem has nothing to do with a VISA alias. You are using an instrument driver? For which instrument? Very old instrument drivers used a different VISA Open. The 'Old' VISA Open needs to be replaced with the current version of VISA Open. You just right click on the function in your initialize VI and select replace. Browse to the VISA>VISA Advanced palette and select the VISA Open that is there. Doing this will create some broken wires. Delete the string control. Often, the VISA reference on the front panel was made invisible so on the diagram, right click on the VISA reference and select 'Show Control'. Make sure that this VISA reference is wired to the VISA resource name input of VISA Open. Go to the front panel of the initialize function and wire the VISA reference to the upper left point of the connector pane. Now, you can just click on the little arrow on the right side of the VISA reference control and get a list of all VISA resources on the system. This will include things like your com ports and GPIB instruments.
If you have any problems, you might want to go ahead and post the VI you are using. It actually takes an experienced LabVIEW programmer less time to make the fix than I just spent typing it all.
