I cannot transfer files from my MacBook to my external hard drive anymore.

I cannot transfer files from my MacBook to my external hard drive anymore. The device responds with error-36 about documents being unreadable and unwritable. Previously the device worked fine.

External Hard Drive

I have an imation Apollo II 2.5" Portable HDD 320GB.

163 GB available.

Macbook

Model Name: MacBook Finder Version 10.6.8

Model Identifier: MacBook6,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.26 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache: 3 MB

Memory: 2 GB

Bus Speed: 1.07 GHz