[Solved] PayPal ERROR - validateIpnContent: Error while posting IPN: , 0

[optmax]

Joomla 2.5.27
VM 2.6.18

and

Joomla 3.4.1
VM 3.0.9.4

My hosting company has just upgraded:
PHP  from version 5.4 to version 5.6
MySQL from 5.5 to 5.6

Nothing else on my sites has changed but...

PayPal orders are no longer having their Order Status set to Confirmed on receipt of the PayPal IPN.

At PayPal the order is confirmed and the IPN HTTP Status Code is 200 - so I assume VM received the IPN but for some reason has not updated the order status.

I receive system emails reporting 'An error with your payment paypal..' and directing me to the error log with entries for each order similar to:
2015-06-15 09:25:11 ERROR validateIpnContent: Error while posting IPN:  ,  0

Before I contact my hosting company can anyone confirm that the PHP/MySQL upgrade may have caused this error - some setting or other maybe?

Or is the PHP/MySQL upgrade coincidental?

Or have PayPal changed something?

[optmax]

Problem fixed by my host.

Some kind of PHP sockets problem - I have no technical details, sorry.