"Fatal error: [] operator" when trying to view active coupon list

Project:Improved coupon discount
Component:Code
Category:
Priority:normal
Assigned:Unassigned
Status:active
Description
Project: 
Discount coupon system

I just started seeing this error when trying to view active coupons:

Fatal error: [] operator not supported for strings in /blahblahmypath/html/sites/all/modules/ubercart/uc_coupon/uc_coupon.module on line 341

I can see only the "Add new coupon" screen and "Inactive Coupons" but I can't see the Active Coupon list; instead I see this error. I am able to add a new coupon (and it shows up in the database, and if I type the URL directly I can get to it to edit), but the Active Coupon list won't display.

What would help to diagnose this? I don't know what exactly has been going on in this site recently (it's an active store, run by a client) but I'd be happy to provide any information about database contents, etc, to track it down.

Thanks!