We have not started testing our products on Windows 7 yet, because it will only be released in about half-year from now (time period that happens to be Veeam's typical release cycle length); besides, many things can still change in it before the actual release. A few Windows 7 specific problem have already been reported for other products, so fully supporting Windows 7 would certainly require some level of development and QC.
Also, please note that some functionality of Veeam Monitor relies on VMware Infrastructure Client presense, and it also cannot be installed on Windows 7. Thus, I would not recommend using Veeam Monitor on Windows 7 at this time.
However, I wanted to check if by any chance you are connecting Veeam Monitor to stand-alone ESXi host while using Advanced Scalability mode, because this would result in "No data available" error on all OS versions (this is documented in the Known Issues section in the release notes document).