Happens from time to time for me on Curve 8330 OS 4.3. I haven't identified any consistent occurrence pattern. The only way I've found to correct it is to refresh the page, which of course removes what's been already composed, so I usually try to copy to the clipboard if I can.
I've read of problems with Curve OS 4.5 but have no experience.
Posted from my CrackBerry at wapforums.crackberry.com
I too have had this issue from time to time. Never could find any sort of pattern to try to figure out what was causing it. You could try getting the bolt browser and use that instead. I've been using it all morning and I'm loving it.
CrackBerry is in no way Affiliated with BlackBerry. We take pride in our unbiased content, however do occasionally receive free products from vendors that we review or discuss. For more info click here.