there is definitly a problem when trying to access to Marketplace through GMS2 IDE
indeed, when I try to open Marketplace from GMS2-IDE, I often have a white screen and the "little blue circle"
at the same time, I have no problem to access the Marketplace through GSM1.4-IDE or using a navigator
I got a white screen also when trying to access the market via the GMS2 IDE. The odd thing was that I could access the marketplace via the browser. That got me thinking it was a firewall issue on my side. I use AVG Internet Security. Now, even though I allowed GMS2 IDE full access (allow all) to the internet, it turns out that even allow all doesn't allow all ports or protocols. When going into AVG's Firewall/ApplicationRules>> I noticed that TCP/UDP in/out was allowed only but had no ports marked as allowed. After setting that ports to 'all' and saving, GMS2 is more stable and the marketplace opens within the IDE with no issues.
So, I guess if you are getting the white screen when trying to access the marketplace via the ide, check your firewall setting and application rules and make sure it definitely is allowed full access.