If you are running a VESA local bus system, you may experience system problems if your motherboard is being run at over the nominal 33 MHz system speed. This includes potential problems if you are using a VESA local bus video card in a VLB/PCI combination motherboard running over 40 MHz.
Some combination VLB/PCI motherboards have difficulties with using the VLB slot or slots that they include. In many cases the engineering on these motherboards is poor, and insufficient testing was done with both the PCI and VESA local buses running simultaneously. The best recommendation is to replace the VLB video card with a PCI one, which are quite inexpensive now.