The only place you are definitely required to prove funds is when you send your application to CIO (or if applied prior to June 26th 2010, when you sent your full docs to visa office).
When you land in Canada to complete your record of landing the immigration officer MAY ask to see proof of funds also (and this must be available and transferrable i.e. in a bank account in CAD, UK sterling, Euro or US dollars, or traveller's cheques etc - so cannot be property valuations at this stage).
In between these two points it is unlikely you will need to show proof of funds, but the visa office MAY ask to see further proof of funds at any point during your application.
Therefore it is highly advisable to keep the entire amount of funds available for your entire application if possible.
Wayne.