Is the front wet at all? If so, check all your front bulkhead grommets........water could be running along something like your bonnet release.........into the car and whats worse, if it is the bonnet release, over your fuse-box

Make sure scuttle drains are clear.
Are you losing any coolant?
Check the windscreen seal at the bottom of your 'A' pillars.
If the front isn't wet, then check the bottom of your door cards, make sure they aren't wet.........if so the membrane needs repairing/replacing.
Whats the boot carpet like? Could be coming in through a poor seal with the rear lights.