This may sometimes get missed, but if your xml nodes are in the format:
<prefix:element />
You need to make sure to set the [namespace or prefix] argument and the [isPrefix] argument to true. Also when recalling elements you need to avoid adding the prefix if that is already set, so in the above example "prefix:element" should be added as "element" but when saved the prefix will be added automatically.
If prefix is not set during load or object construction, load will fail to get the nodes correctly and you will not be able to recall elements directly so $xml->{'prefix:element'} will not work either.
