Payflow payment module not working 1.3.9b

I am working on a fresh install of 1.3.9b and have downloaded and installed the current Payflow add-on module with the sandbox active. When I checkout I receive a blank screen and the following error in the log:

PHP Fatal error: Cannot unset string offsets in .../includes/modules/payment/paypal/paypal_curl.php on line 203

The same payment module works fine on a different store on 1.3.8a. I compared the two paypal_curl.php files using winmerge and they are substantially changed from 1.3.8a to 1.3.9b.

Both installs are running on Server OS: Linux 2.6.33.1 PHP Version: 5.2.13 (Zend: 2.2.0)
IMage handler 2 is the only add-on installed.

Can anybody help with this?

BTW I copied the 1.3.8a version of paypal_curl.php to the new system and checkout works fine but with the number of other changes to the file I'm reluctant to use it.

I see that there's an update to 1.3.9c now. Any chance installing the update might fix this problem? Am I the only Payflow user running Zencart?

I've not the required facilities to test this updated module at the moment, so I'm offering it to you to test using your 1.3.9c site (with the 1.3.9c paypal_curl.php in place).

If you encounter any problems/errors, please post here.

If it works correctly, please also post so that the Addon may be updated for others to benefit from it.

** attachment removed ... can now be obtained from the Addons directory ***

DrByte,
I installed a fresh copy of 1.3.9c with a clean database and tested with the unmodified Payflow add-on from 1.3.8. As expected I got a failure on checkout. I then uninstalled the Payflow add-on and copied the changes you provided in the zipped file. I reinstalled the add-on and tested again. The changes you provided solve the problem and I was able to enter an order and complete the checkout process. Thanks for the help!

Thanks for the confirmation. The addon has been updated.