Post your config, also run "show port congestion", "show port txerrors", and "show port rxerrors" on the uplinks and port going to the laptop that drops ping.
It would depend on your situation. As explained above you can have more than one tagged vlan per port and only one untagged vlan, but how many devices on the vlan? More than 200-300 devices could start impacting performance depending on utilization...
