I just upgraded my DNN install from 5.1.0 to 5.3.1 over the weekend and my event log is rapidly filling up with this error.

AssemblyVersion: 5.3.1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: cc79212f-5a6d-407c-bd94-cca37f90eeed
InnerException: Access to the path '\Cache\Modules\' is denied.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.IO.__Error.WinIOError
StackTrace:
Message: System.UnauthorizedAccessException: Access to the path '\Cache\Modules\' is denied. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.Directory.InternalCreateDirectory(String fullPath, String path, DirectorySecurity dirSecurity) at System.IO.Directory.CreateDirectory(String path, DirectorySecurity directorySecurity) at DotNetNuke.Services.ModuleCache.FileProvider.GetCacheFolder(Int32 portalId) at DotNetNuke.Services.ModuleCache.FileProvider.PurgeExpiredItems(Int32 portalId) at DotNetNuke.Services.ModuleCache.PurgeModuleCache.DoWork()
Source:
Server Name: DIOXWEB

Also, the errors seem to come in a chain: Scheduler Exception (per above), General Exception (same as above; I'm assuming the Scheduler exception did a throw), and a Scheduler Event Failure:

THREAD ID: 6
TYPE: DotNetNuke.Services.ModuleCache.PurgeModuleCache
EXCEPTION: Access to the path '\Cache\Modules\' is denied.
RESCHEDULED FOR: 3/29/2010 8:38:18 AM
SOURCE: STARTED_FROM_BEGIN_REQUEST
ACTIVE THREADS: 1
FREE THREADS: 0
READER TIMEOUTS: 0
WRITER TIMEOUTS: 0
IN PROGRESS: 1
IN QUEUE: 6
Server Name: DIOXWEB

Additional details: 
- I'm hosting with Server Intellect, and using Helm as my control panel
- The portals\0\cache\modules folder existed already
- The portals\_default\cache\modules folder did not exist (the modules folder was missing), but I created that folder via the control panel and it didn't help
- I disabled the 4 or so duplicate 'Purge Cache' tasks so that only one is active
- When I did the upgrade from 5.1.0 to 5.3.1, it hadn't updated the web.config file properly (there's another thread on the forums about this happening to other folks) -- so I had to go in and tweak it by hand, copying/pasting portions to sync up the 5.3.1 release.config into the web.config.

Is there anything else I can do to provide help?

Thanks in advance!
Cliff

I have also been having this problem on a new install (not upgrade) of 5.2.3 at 3Essentials with Plesk.  Will try the suggestions that have been made so far.

Hi All, I too am still looking for a cure for the cache/modules is denied error. I have seen this on multiple installs including new and upgrades, and on new 5.3.1 installs using plesk on PowerDNN.

I do have the cache/modules folder in portals 0+ but it was not created at the root c:/. Indeed interesting how that might get created outside IIS in some cases in local environments.

I'm not a core programmer, but in my experience this started occuring somewhere around 5.2 and up. Seems simple ... the system is trying to access a folder using an incorrect path. I'm surprised the solution has seemed to eluded everyone. There are a lot of posts regarding this and I'm sure hundreds more DNN users having this issue that are not even aware of it.

If I can provide any details to you core DNN guys just let me know I have about a dozen installs on PowerDNN dedicated Win 2003 Server (plesk) ranging from 4.9.5 to 5.3.1. I'd be glad to help resolve as it's driving me nuts too ... and I've seen a few "Out of Memory" errors recently that temporarily crash the installs from time to time ... not sure it's related. But if there's caching problems .. maybe that's what's chewing up my memory.

Thanks

Kelly O