First of all, I would be careful. Thats what is really going to kick up your data usage for the month.
Two, I dont know if there is a limit on the phone itself. Ive downloaded some rather large files without an issue. You may already be exceeding your monthly limit so I would contact the carrier and see what the usage limit is.
I have had the same issue with my 8230. It is mostly when I am trying to download files over 8mb. The browser states that it is two large. I have an unlimited data plan with a 8gb card in the unit.
i have an unlimited plan with my phone so i dont think data would be a problem... im able to download some files so i think it as the post above me said it probably only allowing me to download a certain amount of MB.
I was just wondering is there any way to turn off that limit or set it higher.