Very strange...
Can you open the diagram of the convolution.vi, then double-click on the "Call Library Function Node". What is the Path? (It should be C:\Program Files\National Instruments\LabVIEW 7.0\resource\lvanlys.*).
Could ot be yours points somewhere else?
Now find the lvanlys.dll in explorer. The size of the LabVIEW 7.0 version should be 528384 bytes.
Do a search for lvanlys.dll. How many different versions show up?