Palm’s Centro might be a big hit, but lower sales of Windows Mobile-based Treos and declines in other handheld products led to reduced revenues for Palm’s fourth fiscal quarter.

Revenue was down about 26% in the quarter. Net loss applicable to common shareholders for the fourth fiscal quarter was $43.4 million.

In a conference call with analysts, President and CEO Ed Colligan said the company expects to deliver revenue growth in the coming quarter, but the company likely will remain unprofitable as it continues to invest in core development and marketing programs.

He called the Centro a “smash” success; it’s drawing new, mostly traditional cell phone users as opposed to long-time Treo enthusiasts, but the Centro is being sold at a lower price. Verizon Wireless launched the Centro earlier this month for $99.99 after rebate.

Palm expects to refresh its Windows Mobile product line soon and to continue to expand product offerings into this fall. Asked if there is potential for new products to get delayed further, Colligan noted that Palm has been working hard to rebuild its team and make sure it has the best talent so any execution issues that may have happened in the past get mitigated. “I’m more confident than ever that this team that’s here today … is going to do not only outstanding products but deliver them on time in the future,” he said.

AT&T, Sprint and Verizon each offer the Centro.

Palm’s shares were trading down more than 6% this morning, at $6.11.