InternalApiError.UNEXPECTED_INTERNAL_API_ERROR when using C# AdWords library to get keyword ideas

Question

I was experimenting with Google AdWords' TargetingIdeaService to load keyword ideas based on a supplied keyword. I was exploring Requested Attribute Types and everything was going well. Then, all of a sudden I started getting InternalApiError.UNEXPECTED_INTERNAL_API_ERROR when doing the same requests. Since the only change I made between a good and a bad request was adding APPROX_CONTENT_IMPRESSIONS_PER_DAY Attrbitue Type, I removed it but to no avail. All subsequent calls end with the same error. I should also mention I'm doing it in the sandbox.

Here's my code:

try
{
       AdWordsUser user = new AdWordsUser();
       TargetingIdeaService tasService =
(TargetingIdeaService)user.GetService(AdWordsService.v200909.TargetingIdeaService);

       // Obtain keyword
       Console.Write("Enter keyword: ");
       string keywordText = Console.ReadLine();

       Keyword keyword = new Keyword();
       keyword.text = keywordText;
       keyword.matchTypeSpecified = true;
       keyword.matchType = KeywordMatchType.BROAD;

       RelatedToKeywordSearchParameter searchParam = new
RelatedToKeywordSearchParameter();
       searchParam.keywords = new Keyword[] { keyword };

       Paging paging = new Paging();
       paging.numberResultsSpecified = true;
       paging.startIndex = 0;
       paging.numberResultsSpecified = true;
       paging.numberResults = 10;

       TargetingIdeaSelector selector = new TargetingIdeaSelector();
       selector.searchParameters = new SearchParameter[] { searchParam };
       selector.ideaTypeSpecified = true;
       selector.ideaType = IdeaType.KEYWORD;
       selector.requestTypeSpecified = true;
       selector.requestType = RequestType.IDEAS;
       selector.paging = paging;
       selector.requestedAttributeTypes = new AttributeType[] {
               AttributeType.AD_SHARE,
               AttributeType.COMPETITION,
               AttributeType.GLOBAL_MONTHLY_SEARCHES,
               AttributeType.KEYWORD,
               AttributeType.SEARCH_SHARE,
               AttributeType.TARGETED_MONTHLY_SEARCHES,
               AttributeType.APPROX_CONTENT_IMPRESSIONS_PER_DAY
       };

       TargetingIdeaPage page = tasService.get(selector);

       if (page != null && page.entries != null)
       {
               Console.WriteLine("There are a total of {0} keywords related to
'{1}'. The first {2}" +
                                                       " entries are displayed below: \n", page.totalNumEntries,
keywordText,
                                                       page.entries.Length);

               foreach (TargetingIdea idea in page.entries)
               {
                       Console.WriteLine("************");
                       foreach (Type_AttributeMapEntry entry in idea.data)
                       {
                               switch (entry.key)
                               {
                                       case AttributeType.KEYWORD:
                                               Console.WriteLine("KW: " +
((KeywordAttribute)entry.value).value.text);
                                               break;
                                       case AttributeType.AD_SHARE:
                                               Console.WriteLine("Ad share: " +
((DoubleAttribute)entry.value).value);
                                               break;
                                       case AttributeType.COMPETITION:
                                               Console.WriteLine("Competition: " +
((DoubleAttribute)entry.value).value);
                                               break;
                                       case AttributeType.GLOBAL_MONTHLY_SEARCHES:
                                               Console.WriteLine("Global Monthly searches: " +
((LongAttribute)entry.value).value);
                                               break;
                               }
                       }
                       Console.WriteLine("************\n===");
               }
       }
       else
       {
               Console.WriteLine("No related keywords were found for your
keyword.");
       }
}
catch (Exception ex)
{
       Console.WriteLine("Error retrieving kw ideas: " + ex.Message);
}

Any ideas as to what could be going wrong?

I'll gladly post request and response data as soon as I find an easy way to extract it.