Cannot recover from permissions removal

We have a SharePoint 2010 site which appears "nuked" after all permisisons were accidentally removed:

• Accessing the site as a normal user or a Site/Farm administrator results in a: 500 INTERNAL SERVER ERROR
• Accessing the _layouts/settings.aspx page results in a: 403 FORBIDDEN.
• Accessing the site with powershell yields:
  
  PS C:\> $web = Get-SPWeb "http://url/site/ subsite"
  Get-SPWeb : Cannot find an SPWeb object with Id or Url : http://url/site/subsite and site Url http://url .
  At line:1 char:17
  + $web = Get-SPWeb <<<<  "http://url/site/subsite"
      + CategoryInfo          :InvalidData : (Microsoft.Share....SPCmdletGetWeb:SPCmdletGetWeb) [Get-SPWeb], SPCmdletPipeBindException
• Accessing the parent Web site ($web.Webs[5]) shows the site and we can see it's Site Title ($web.Webs[5].Title), however any security-related operations fail (e.g. BreakRoleInheritance($true), Permissions.ResetPermissions, Roles Collection)... with this error: The following exception was thrown when trying to enumerate the collection: "Cannot complete this action.
  Please try again.".
  At line:1 char:14
  + $web.Webs[5]. <<<< Roles
      + CategoryInfo          : NotSpecified: (:) [], ExtendedTypeSystemException
      + FullyQualifiedErrorId : ExceptionInGetEnumerator
• Accessing "PS C:\> $web.Webs[5].Webs" causes this error:
  Cannot index into a null array.
• This is all I can really find in the ULS logs:
  
  11/22/2010 15:36:22.18  PowerShell.exe (0x128C)                  0x0AC8 SharePoint Foundation          General                       8kh7 High     Cannot complete this action.  Please try again.<nativehr>0x80004005</nativehr><nativestack></nativestack> e484e439-f403-45d1-bf20-fd84437542e4
  11/22/2010 15:36:22.18  PowerShell.exe (0x128C)                  0x0AC8 SharePoint Foundation          PowerShell                    6tf2 High     Cannot find an SPWeb object with Id or Url : http://url/site/subsite and site Url http://url. e484e439-f403-45d1-bf20-fd84437542e4
  11/22/2010 15:36:22.18  PowerShell.exe (0x128C)                  0x0AC8 SharePoint Foundation          PowerShell                    91ux High     Error Category: InvalidData   Target Object  Microsoft.SharePoint.PowerShell.SPCmdletGetWeb  Details  NULL  RecommendedAction NULL e484e439-f403-45d1-bf20-fd84437542e4

We have requested a content database restore (losing a day of content) as we can't wait for a fix.

But for future reference, is there any way to recover for this error?