Should a move or upgrade effect traffic to a site ?

[PatF]

I've a bit of a strange one. We moved a number of our sites from one server to another (new host) Two of these are Zencart sites (one of which - the problematic one is hosted on behalf of someone else)

As part of the move his sites was upgraded to 1.3.9h from 1.3.8a as the new server ran PHP 5.3 and his old site would not run on it.

So since the move traffic on his site (from zencart admin page information) is down 40% - 50%.

Our own site which moved from the same set of servers but was not upgraded has had no noticable drop in traffic. Both sites went into maintenance mode / offline for the same period etc.

I checked DNS settings and pathways etc via online tools and there are no issues.

So I'm wondering would search engines see an upgraded page (same content - same database etc) as a "new" page and show the old version of the pages (from the old site) as being deleted ?

Has anyone come across this before ?

[schoolboy]

I must have moved over 100 ZC sites since 2004, and on many of these an upgrade was done on the way.

Never experienced a drop in SE ranking, nor a drop in visitors. Google pays no attention to the "mechanics" of where a site lives - unless of course the new server is mal-configured and is giving poor data (such as Headers).

Where are you hosting?