You might want to try updating to System 7.5.5.  It's a free update, and probably compatible with your iix. 

More importantly, have you tried installing this driver?:  http://www.vintageapple.org/macdrivers/nic/Shiva_Kinetics_Novell.hqx

LazarusNine said:

My OS is System 7.5.3 (unfortunately 7.6 isn't compatible with the IIx).

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