Internal Server Error when editing product

[DWNY]

I'm working on a PrestaShop installation for a client, and he ran into a problem yesterday while trying to edit a product.

 

After updating the information, clicking either 'Save & Stay' or 'Save' returns a 500 Internal Server Error. I looked at the error log and here are the last two errors recorded:

Stack trace:
#0 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_cacheresource_file.php(102): Smarty_Internal_Write_File::writeFile('/home/webcat/pu...', '<?php /*%%Smart...', Object(Smarty))
#1 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_cacheresource.php(367): Smarty_Internal_CacheResource_File->writeCachedContent(Object(Smarty_Internal_Template), '<?php /*%%Smart...')
#2 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_template.php(230): Smarty_Template_Cached->write(Object(Smarty_Internal_Template), '<?php /*%%Smart...')
#3 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_templatebase.php(259): Smarty_Internal_Template->writeCachedCon in /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_write_file.php on line 44
[18-Sep-2014 09:39:24 US/Eastern] PHP Fatal error:  Uncaught exception 'SmartyException' with message 'unable to write file /home/webcat/public_html/presta/cache/smarty/cache/20938/1/21/09/b1/86/wrt541ae08cbfe4f9.95381143' in /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_write_file.php:44

Stack trace:
#0 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_cacheresource_file.php(102): Smarty_Internal_Write_File::writeFile('/home/webcat/pu...', '<?php /*%%Smart...', Object(Smarty))
#1 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_cacheresource.php(367): Smarty_Internal_CacheResource_File->writeCachedContent(Object(Smarty_Internal_Template), '<?php /*%%Smart...')
#2 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_template.php(230): Smarty_Template_Cached->write(Object(Smarty_Internal_Template), '<?php /*%%Smart...')
#3 /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_templatebase.php(259): Smarty_Internal_Template->writeCachedContent('')
#4 /home/webcat/p in /home/webcat/public_html/presta/tools/smarty/sysplugins/smarty_internal_write_file.php on line 44

You'll notice that the last error has an extra line (#4) with what looks like a path error. The error recorded prior to it does not have that extra line.

 

Anyone have any ideas what could be causing this, and how to remedy the problem. I appreciate any help you can give.

Edited September 18, 2014 by DWNY (see edit history)