what is being shared with the vid card?
Is there a card in the pci slot next to the agp/pcie slot? If so you might try moveing it to another slot. Some motherboards will share the same irq between the agp slot and pci slot 1. You might look in the motherboard manual and see if it lists the irq that each slot uses and arrange you cards to try and avoid sharing on the most used cards.
These days almost all devices in a computer will share IRQ's. I wouldn't be worried. PCI is a 32bit interface and is good at sharing. Back in the ISA & early PCI days sharing IRQ 16 (which was mostly designated for video cards) was not a good idea... it either didn't work or didn't work well (EISA was able to share IRQ's as well). Win95 also did a crap job of assigning IRQ's. That was fixed in WinxP Anyways, it doesn't matter anymore.
If you don't have an stability problems then don't worry about it.