After upgrade can't view any customer invoices

I have had my install running for years with little issues, I have upgraded successfully many many times and this last upgrade i thought i did what i normally do but I guess i didn't.

A customer just got in touch with me and said they can't view their invoices so when i try and go to the PDF version of their invoice i get a internal server error. ????

Checked the file permissions they are all 644, php member was 64 MB upped it to 128 MB.

Everything else is working, Ticketing system, cron jobs,

I do this this error when started to happen around the time i upgraded tot he newest version of whmcs.

[Tue Apr 22 22:13:36 2014] [error] [client XXX.XXX.XXX.XX] ] [notice] EACCELERATOR(12410): PHP crashed on opline 55 of loadClass() at /home/blah/public_html/support/includes/classes/WHMCS/Application.php:0, referer:

/http://websitehere.com/support/doodoo/invoices.php?action=edit&id=659

i'd be tempted to upload the "includes" folder again from the latest full release and see if that fixes the issue.

I uploaded the entire site again and that didn't work, everything else is working.

root@ec03 [~]# php -v

PHP 5.4.27 (cli) (built: Apr 23 2014 00:16:44)

Copyright © 1997-2014 The PHP Group

Zend Engine v2.4.0, Copyright © 1998-2014 Zend Technologies

with eAccelerator v0.9.6.1-ea, Copyright © 2004-2012 eAccelerator, by eAccelerator

with the ionCube PHP Loader v4.4.1, Copyright © 2002-2013, by ionCube Ltd.

fixed the issue by uninstalling EACCELERATOR

Did you try installing eaccelerator again ? (or any other cache system? )