To update your phone, you just do it by the ota way. There may be a notification (I am not sure), or you can check by going into settings and finding it (I honestly can not remember, I have a great rom that does not have the update option because you have to update it manually). If you want to fix this problem right away, like i said before go ahead and install this rom [ROM] Infused v2.1.0 - (08/27) - xda-developers
if you want it fixed and the newest operating system on your Infuse. The app store is having problems installing apps, because google is waiting for Samsung to fix it. Samsung probably will not for a while, but a minor fix is to go into settings, then applications, then manage tap on the all tab, find the market and clear data. This can also fix market problems if there are any others, even if you install another rom.