Scanner stops working for no apparent reason

I am using Vista Home Premium on a Sony Vaio desktop PGC-282M

I have a CanoScan LiDE30 (B/W, flatbed) scanner. Worked perfectly until 13 February 2009.

On that day, I used my HP Photosmart C4380 to make a colour copy of a brochure. Hitherto HP used only by me as a printer and occasional scanner. Googled my way into trying various remedies, including - attempts to go to a Restore point having failed - removing various recently-added programmes (in case of conflicts) and all HP software. Then deleted and reloaded from original disc the software for Lide30 and updated drivers.
All that happened was that instead of getting the message 'Unable to SELECT Twain source', as before, I now get the message 'Unable to OPEN Twain source. Please check connection'. Needless to say, I have re-checked my connections many times!

Advice please!!!