Add new field does not show custom fields created with CCK + Whitescreen error when trying to add no results behaviour

I have used CCK to create a number of content types and content fields. I have lots of views which use these fields. Something appears to have gone horribly wrong - when I try to edit an existing view and click 'add field' I can only choose from default content fields such as 'Content: Title', 'Content: Type', 'Content: Post date' - now none of the fields I created with CCK are available in the list.

If I create a new view and try to add a field, all of the fields (including the fields I created with CCK) are available, so in this scenario everything works fine. Creating a clone of an existing view also makes all the fields available when it is first created, but coming back to edit it later, it becomes like the existing views and only default fields are available.

In addition if in an existing view I try to add a 'no results behavior' I get told 'There are no no results behavior available to add.' If ignore this and click the 'Add and configure no results behavior' button anyway. I get a white screen with an error message beginning:

[{"command":"settings","settings":{"basePath":"\/","pathPrefix":"","ajaxPageState":{"theme":"seven","theme_token":"kNuAuwAyruWbQMh31fVXVzkCihNcVzsLPyzAmLGHDNc"},"beautytips":{"beautytips":{"fill":"#F7F7F7","padding":8,"strokeStyle":"#B7B7B7","cornerRadius":0,"cssStyles":{"fontFamily":"\u0026quot;lucida grande\u0026quot;,tahoma,verdana,arial,sans-serif","fontSize":"11px"},"cssSelect":"beautytips","list":["fill","padding","strokeStyle","cornerRadius","cssStyles"]},".beautytips": ...trimmed for brevity...

Again if i start a new view this issue does not occur and adding a 'no results behavior' gives the usual options. The above error mentions the beauty tips module. I have tried disabling this module - doing this this means I don't see the initial beauty tips related code from the start of the white screen text, but the problem still occurs with a shorter error message.

I am guessing that this problem may be quite involved, so I would really appreciate some advice on where/how to start investigating the problem. Please let me know if there is additional information I can provide that would be helpful.

I have combined the two issues 'Add new field does not show custom fields created with CCK' + 'Whitescreen error when trying to add no results behaviour' into this one issue as i suspect that they may be connected. If this is not the correct approach, please let me know.