With ten of them there's a good chance that you're exceeding the switch's maximum power rating. i.e. 10 75 watt bulbs would be 750 watts which would be too much for the standard switches (usually 500 or 600 watt ratings).

You can upgrade to a high-wattage switch such as the PCS PCSS1L/S-1000 which is rated up to 1000 watts, and still provides dimming and silent operation, for $68.20. Alternately, you could go with a relay module, typically used for ceiling fans or flourescent lights. The X10 Pro XPS3 is rated for 20A at 120V, which converts to 2,400 Watts (P=I*E), for $27.89. What you'd lose is the ability to dim the lights and you will have an audible "thunk" when the switch is activated.

You can see all the X10 receivers I mentioned at this URL: [Link: homeautomationnet.com] Just figure out what your total power capacity needs are then you can pick the switch that'll do the job.