was inbound to Winnipeg from God's Lake Narrows with the pilot and 4 passengers. When the a/c was about 10 miles northwest of Winnipeg, the pilot reported to ATC that there was smoke in the cockpit. ERS was activated while the a/c landed on Runway 13 at 2155Z. The ERS stood down shortly after the a/c landed and there was no reported evidence of a fire or damage to the a/c. Maintenance reports that when the smoke appeared in the cockpit, the pilot noticed that the circuit breaker for the lip boots on the engine intakes had popped. The a/c is presently at an AMO and the electrical system is being examined to determine the reason for the problem. OPI - System Safety UPDATE Maintenance reported that after 3 days of inspecting all of the electrical wiring in the cockpit, they have been unable to determine the exact cause of the smoke. There is no evidence of any burned or charred wiring anywhere. The lip boot on the number 1 engine had hardened and delaminated, causing the boot to become brittle and flake off. Small pieces of the boot were found in the engine intake screen, the largest piece being thumbnail size. The boot has been replaced and the a/c has been test flown for 2 hours with no recurrence.