Patrick - an investor has most of the time three stages
1) If very interested, will work with you and invest NOW if it is clear that this is a now or much later situation
In this case he or she will pull in one or two other investors to carry the risk with them
2) Is kind of interested - will wait until there are others in as well and it is a now or never situation
3) Is dragging their feet - not really interesting - you basically are just an annoyance
In other words if he is the only and you don't have others lined up - he will not move and you should work on either your fundraising strategy or more likely actually on your business model or other things around your company so you attract multiple investors.