You can remove stored downloads in the location where they are stored (probably ~/Downloads).

I cannot find any file looking like that. I have been advised elsewhere that /tmp might be overfull but that is not the case either. Problem still persists which is very distressing since I am not able to download anything. Anyone else having ideas??

Further to this sad saga, I have also discovered that another effect has been that when closing down ubuntu normally, I do not get the usual option panel offering restart or shut-down and select the latter it does not happen but the ubuntu page reappears but with no top panel with the icons on it. I have to shut the computer down with a long hold of the power on button. So the problem must have got into Ubuntu proper as well as the download part of Firefox. Any ideas out there ?????

Your Download database on Firefox profile may be corrupted. Ensure Firefox is closed, open ~/.mozilla/firefox/xxxxxxxx.default/ in Nautilus (the xxx there is random strings, but it should be only one folder inside /firefox/), then delete the "downloads.sqlite" file.

Problem identified at last! I used Simple Backup in Ubuntu 8.04 to store backup files on to USB sticks on several occasions. Unwittingly this resulted in the storage of large files within some Trash folders on the computer to the extent that the HD became full. This has screwed up Ubuntu more that somewhat with many features no longer working including the Download of Firefox and anything that involves saving. Arun's blog says that he has suffered the same problem. Forum posts elsewhere show that this is a result of a bug within Simple Backup. There is no indication of a workround or cure. Regretfully I am having to scrap my OS and start again because I seem unable to locate the erroneous files for deletion. I will be taking the opportunity to update 8.04 to 10.04 for the installation. Luckily I do have BU copies of the important parts so should not be left high & dry.

Wish me luck!!

I am still wrestling with this problem, time not been on my side for what seems to be a time consuming job. I mentioned that I have not been able locate the Trash files that Arun identified in his blog (www.blog.arun-prabha.com/2008/07/22/deleting files...) but he did not say how he deleted them. I have failed to correctly identify them on my machine, perhaps the dog-eared state of 8.04 is stopping me. Although I had the full address for the files using sudo find, typing them into the search elemnt of Nautilus could not find them. Could it be as they are hidden and Nautilus does not seem to allow for sudo openration?

Others look as though they have had the same problem, perhaps you or one of them can explain?

IMO, if your problem is still with Firefox crashing when you attempt to open Downloads, you should just delete the file where Firefox stores that download information - downloads.sqlite.

daikirai mentioned that on January 7th.

Delete downloads.sqlite (plus downloads.rdf, if it exists) in the Profile Folder

See http://kb.mozillazine.org/Unable_to_save_or_download_files#Manually_delete_download_history

Help > Troubleshooting Information > Profile Directory: Open Containing Folder

Thanks for the refs, I appreciate persons of such vast anounts of postings taking an interest in us amateurs! I will follow your advice but the Arun ref I mentioned clearly illustrates my problem. Perhaps it is not fair of me to think that this forum is the right place to air my woes. But I will keep in touch.